Science · Textbook solutions

Magnetic Effects of Electric Current

Every solved example, exercise, and miscellaneous question, in the order the textbook teaches them. Plus every board question asked from this chapter. · 25 questions

12.1 Magnetic Field and Field Lines

1 q

Question

Practice · 1

IT 12.1 Q1 $Why does a compass needle get deflected when brought near a bar magnet?$

12.2.2 Right-Hand Thumb Rule

4 q

Solved Examples

Worked · 1

12.2 Eg.1 $A current through a horizontal power line flows in east to west direction. What is the direction of magnetic field at a point directly below it and at a point directly above it?$

Questions

Practice · 3

IT 12.2 Q1 $Draw magnetic field lines around a bar magnet.$
IT 12.2 Q2 $List the properties of magnetic field lines.$
IT 12.2 Q3 $Why don't two magnetic field lines intersect each other?$

12.2.4 Magnetic Field due to a Current in a Solenoid

3 q

Questions

Practice · 3

IT 12.3 Q1 $Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.$
IT 12.3 Q2 $The magnetic field in a given region is uniform. Draw a diagram to represent it.$
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IT 12.3 Q3 $The magnetic field inside a long straight solenoid-carrying current$
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12.3 Force on a Current-Carrying Conductor in a Magnetic Field

4 q

Solved Examples

Worked · 1

12.4 Eg.2 $An electron enters a magnetic field at right angles to it, as shown in Fig. 12.14. The direction of force acting on the electron will be (a) to the right. (b) to the left. (c) out of the page. (d) into the page.$

Questions

Practice · 3

IT 12.4 Q1 $Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.) (a) mass (b) speed (c) velocity (d) momentum$
IT 12.4 Q2 $In Activity 12.7, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?$
IT 12.4 Q3 $A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is$
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12.4 Domestic Electric Circuits

3 q

Questions

Practice · 3

IT 12.5 Q1 $Name two safety measures commonly used in electric circuits and appliances.$
IT 12.5 Q2 $An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.$
IT 12.5 Q3 $What precaution should be taken to avoid the overloading of domestic electric circuits?$

Exercises

10 q

Ex 12 Q1 $Which of the following correctly describes the magnetic field near a long straight wire?$
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Ex 12 Q2 $At the time of short circuit, the current in the circuit$
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State whether the following statements are true or false.
Ex 12 Q3 (a) $The field at the centre of a long circular coil carrying current will be parallel straight lines.$
Ex 12 Q3 (b) $A wire with a green insulation is usually the live wire of an electric supply.$
Ex 12 Q4 $List two methods of producing magnetic fields.$
Ex 12 Q5 $When is the force experienced by a current-carrying conductor placed in a magnetic field largest?$
Ex 12 Q6 $Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?$
Ex 12 Q7 $State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current, (ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (iii) current induced in a coil due to its rotation in a magnetic field.$
Ex 12 Q8 $When does an electric short circuit occur?$
Ex 12 Q9 $What is the function of an earth wire? Why is it necessary to earth metallic appliances?$

What the board has asked from this chapter

Questions per paper · 67 papers · 2022 to 2026

2026

26 q

For Question number 32, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to this question from the codes (A), (B), (C) and (D) as given below.
32 $Assertion (A) : The needle of a compass, kept in an external magnetic field, always aligns itself in the North-South direction of the Earth. Reason (R) : The behaviour of the needle of the compass is similar to the behaviour of a freely suspended bar magnet.$
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Magnetic Field and Field Lines
For Question number 32, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to this question from the codes (A), (B), (C) and (D) as given below.
32 $Assertion (A) : Direction of force exerted on a current-carrying conductor placed in a magnetic field remains same if the directions of both magnetic field and current flowing through the conductor are reversed. Reason (R) : The direction of force exerted on a current-carrying conductor placed in an external magnetic field can be determined by using magnetic compass.$
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Force on a Current-carrying Conductor
Direction : For question number 32, two statements are given – one labelled as Assertion (A) and other labelled as Reason (R). Select the correct answer to this question from the codes (A), (B), (C) & (D) as given below :
32 $Assertion (A) : With the help of compass, magnetic field lines can be traced outside the bar magnet. Reason (R) : The north pole of a compass needle always points towards the south pole of the magnet when brought close to it.$
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Magnetic Field and Field Lines
For question number 32, two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to this question from the codes (A), (B), (C) and (D) as given below :
32 $Assertion (A) : The needle of a magnetic compass kept in strong external magnetic field, always aligns itself in north-south direction on the earth. Reason (R) : Behaviour of the needle of a compass is same as that of a freely suspended bar magnet.$
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Magnetic Field and Field Lines
33 (B) $How is an electromagnet made ? Write any two ways by which the strength of electromagnet can be increased.$
Magnetic Field due to a Solenoid
36 $(a) Describe an activity to show that a current carrying conductor, placed in an external magnetic field experiences a force. (b) Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally towards the front wall from the back wall, is deflected by a strong magnetic field to your right side. Find the direction of the magnetic field.$
Force on a Current-carrying Conductor
37 $(a) The pattern of magnetic field due to a current carrying wire depends upon the shape made by that wire. Justify. (b) A current carrying straight wire AB is shown in the given diagram. Out of X, Y and Z on which point will the strength of magnetic field be maximum and why ?$
Magnetic Field due to a Current-carrying Conductor
37 $On the basis of the given circuit arrangement, answer the following questions : (a) What happens to the rod AB when the key K is closed and why ? (b) Name and state the rule that determines this behaviour of the rod AB in the above situation.$
Force on a Current-carrying Conductor
39 (a) $(i) What is a solenoid ? Draw a diagram showing the magnetic field pattern due to a current-carrying solenoid (inside and outside). (ii) Name any two factors on which the magnitude of the magnetic field due to a current-carrying solenoid depends. (iii) A current-carrying solenoid is stretched and converted into a straight wire carrying current. Draw a diagram showing the magnetic field pattern around it and mark the direction of the magnetic field.$
Magnetic Field due to a Solenoid
39 (a) $(i) Write the name and statement of the rule used to determine the direction of the : (I) force experienced by a straight current-carrying conductor placed in a uniform magnetic field perpendicular to the field. (II) magnetic field produced around a straight conductor carrying electric current. (ii) Differentiate between the magnetic field due to a bar magnet and the magnetic field due to a current-carrying solenoid.$
Magnetic Field due to a Current-carrying Conductor
39 (a) $A person was repairing an electric heater. He observed that there were three different connecting wires of three different colours in the cable attached to the heater. (i) What are these three different wires called ? Name them colourwise. (ii) What is the value of standard potential difference at which electricity is supplied in Indian homes for lighting ? (iii) What is the role of (I) earthing and (II) fuse in domestic electric circuits ?$
Domestic Electric Circuits
39 (b) $(i) With the help of a diagram, show that a current-carrying conductor placed in an external magnetic field, experiences a force. Indicate the direction of the field, current and force clearly. (ii) The diagram given below shows an electron moving in a uniform magnetic field. (I) What will be the direction of the force acting on the electron ? (II) What will happen to the direction of the force acting on the electron, if the direction of the magnetic field as well as the direction of motion of the electron, both are reversed ?$
Force on a Current-carrying Conductor
39 (b) $(i) With the help of a diagram, describe an activity in brief to show that a current-carrying straight conductor produces a magnetic field around it. (ii) Two straight current-carrying conductors (A) and (B) are shown in the figures below : (I) Mark the direction of the magnetic fields around these current-carrying conductors (A) and (B). (II) Compare the strengths of magnetic fields produced (1) at points P and Q and (2) at points Q and R due to these current-carrying conductors, qualitatively.$
Magnetic Field due to a Current-carrying Conductor
39 (b) $(i) Write the name and statement of the rule used to determine the direction of the : (I) force experienced by a straight current-carrying conductor placed in a uniform magnetic field perpendicular to the field. (II) magnetic field produced around a straight conductor carrying electric current. (ii) Two straight current-carrying conductors (A) and (B) are shown in the figures below : (I) Mark the direction of the magnetic fields around these current-carrying conductors (A) and (B). (II) Compare the strengths of magnetic fields produced (1) at points P and Q and (2) at points Q and R due to these current-carrying conductors, qualitatively.$
Magnetic Field due to a Current-carrying Conductor
39 (a) $(i) State the rules to determine the following : (I) Direction of magnetic field produced around a current-carrying straight conductor. (II) Direction of force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it. (ii) (I) Draw the magnetic field lines due to a current-carrying solenoid. (II) Three points A, B and C are marked in the above given diagram of the current-carrying solenoid. Out of the three points A, B and C, at which point is the magnetic field strength maximum and at which point is it minimum ?$
Magnetic Field due to a Solenoid
39 (a) $(i) The magnetic field lines due to two bar magnets X and Y are shown in the given diagram. If the magnet X is displaced towards magnet Y, will there be repulsion or attraction between them ? Justify. (ii) A metallic conductor is suspended perpendicular to the magnetic field of a horseshoe magnet. The conductor gets displaced towards the left when a current is passed through it. What will be the effect on displacement of conductor if the : (I) Current through the conductor is increased ? (II) Horseshoe magnet is replaced by another stronger horseshoe magnet ? (III) Direction of current through the conductor is reversed ?$
Force on a Current-carrying Conductor
39 (A) $(i) Draw a diagram showing the magnetic field lines around a bar magnet. Write any two characteristics of magnetic field lines. (ii) Write the statement of Right hand thumb rule. (iii) The concentric circles representing the magnetic field around a current carrying straight wire become larger and larger as we move away from the wire. How does magnetic field change on these concentric circles ?$
Magnetic Field and Field Lines
39 (A) $(i) List any two features of the electric current used in the houses of India. (ii) Write any two differences between direct current and an alternating current. (iii) How will you identify live wire and neutral wire in a domestic electric circuit ?$
Domestic Electric Circuits
39 (a) $(i) State the rule which gives the direction of force acting on a current-carrying conductor placed in a magnetic field. (ii) What is a fuse ? Why is it called a safety device ? (iii) Why are electrical appliances with metallic bodies connected to the mains through a three-pin plug, whereas an electric bulb is connected with a two-pin plug ? (iv) What will be the direction of force experienced by the conductor AB due to the magnetic field, when current flows in the direction shown ? Name the law you applied to find the direction.$
Force on a Current-carrying Conductor
39 (A) $(i) State the rule which gives the direction of force acting on a current carrying conductor placed in a uniform magnetic field. (ii) Name any two devices which work on the basis of an interaction between magnetic field and current carrying conductor. (iii) Observe the given diagrams : Comment on the magnitude of force on electron in both the cases and give reason for your answer.$
Force on a Current-carrying Conductor
39 (B) $(i) List three possible reasons of short-circuiting in an electric circuit. (ii) In case of overload, will the fuse protect to given electric circuit from damage ? Justify your answer. (iii) For an electric heater rated as 220 V, 2200 W, what should be the minimum rating of fuse used with it ?$
Domestic Electric Circuits
39 (b) $(i) Draw a schematic diagram of a domestic electric circuit which includes the following devices : (I) A fuse (II) A power meter (III) One light point (IV) A power plug (ii) Why is it necessary to connect an earth wire to the electrical appliances having metallic covers ?$
Domestic Electric Circuits
39 (b) $(i) Draw the pattern of magnetic field lines through and around a current-carrying circular loop. (ii) State the rule to find out the direction of the magnetic field inside and around the circular loop. (iii) Give reasons : (I) Why should a burnt-out fuse be replaced by another fuse of identical rating only, in an electric circuit ? (II) Why is soft iron-core used in making an electromagnet ?$
Magnetic Field due to a Current-carrying Conductor
39 (B) $(i) Why is fuse an important component in our electric circuits ? (ii) Distinguish between overloading and short-circuiting of a circuit. (iii) Giving reason explain what type of materials are used in fuse wires.$
Domestic Electric Circuits
39 (B) $(i) Draw a diagram, showing the magnetic field lines in and around the current carrying solenoid. Write any two salient features of these lines. (ii) What is an electromagnet and how is it made ?$
Magnetic Field due to a Solenoid
39 (b) $B$
Magnetic Field due to a Current-carrying Conductor

2025

32 q

13 $In domestic electric circuits, the colour of insulation covers of wires in the cables of electric iron/electric toaster is generally :$
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Domestic Electric Circuits
14 $Which one of the following statements is not true about a bar magnet ?$
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Magnetic Field and Field Lines
15 $The strength of the magnetic field produced inside a current carrying long straight solenoid does not depend upon :$
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Magnetic Field due to a Solenoid
15 $The strength of magnetic field produced inside a long straight current carrying solenoid does not depend upon :$
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Magnetic Field due to a Solenoid
For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
19 $Assertion (A) : No two magnetic field lines are found to cross each other. Reason (R) : The compass needle cannot point towards two directions at the point of intersection of two magnetic field lines.$
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Magnetic Field and Field Lines
For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
19 $Assertion (A) : Magnetic field lines around a bar magnet never intersect each other. Reason (R) : Magnetic field produced by a bar magnet is a quantity that has both magnitude and direction.$
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Magnetic Field and Field Lines
Q. Nos. 17 to 20, two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below :
19 $Assertion (A) : In the common domestic circuits the earth wire is connected to a metallic plate buried deep inside the earth. Reason (R) : Earth wire ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, so the user may not get a severe electric shock.$
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Domestic Electric Circuits
Question Nos. 17 to 20 consists of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option from (A), (B), (C) and (D) given below :
19 $Assertion (A) : The pattern of the magnetic field of a solenoid carrying a current is similar to that of a bar magnet. Reason (R) : The pattern of the magnetic field around a current carrying conductor is independent of the shape of the conductor.$
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Magnetic Field due to a Solenoid
26 $Draw the pattern of magnetic field lines due to a current carrying straight conductor. Mark on it the direction of current in the conductor and the direction of the magnetic field developed. Name the rule that helps us to determine the direction of magnetic field lines in this case.$
Magnetic Field due to a Current-carrying Conductor
26 $What are magnetic field lines. List two important properties of magnetic field lines.$
Magnetic Field and Field Lines
27 $What is short circuiting ? State its possible causes. What is likely to happen if a domestic circuit gets short circuited ? Give reason for the justification of your answer.$
Domestic Electric Circuits
27 $Answer the following questions for a case in which a current carrying conductor is placed in a uniform magnetic field : (a) List three factors on which the magnitude of the force acting on the conductor depends. (b) When is the magnitude of force on the conductor maximum ? (c) Name the rule which helps in determining the direction of force on the conductor and give its one application.$
Force on a Current-carrying Conductor
32 $Consider a rectangular cardboard having two holes P and Q through which a current carrying circular loop has been inserted as shown in the diagram. (a) Make this diagram on your answer sheet and draw three magnetic field lines, one each passing through the points 1 (near P), 2 (at the centre of the loop) and 3 (near Q). (b) List two factors on which the intensity of the magnetic field produced at the centre of the loop depends. (c) Name the rule you will apply to determine the direction of magnetic field produced due to a current carrying straight conductor.$
Magnetic Field due to a Current-carrying Conductor
32 $(a) Draw a labelled diagram to show the pattern of magnetic field lines on a horizontal white board due to a straight current carrying conductor passing perpendicular through its centre. If the direction of current in the conductor is vertically downwards, mark the direction of (i) current, and (ii) magnetic field lines. (b) State the right hand thumb rule and check whether the directions marked on the diagram are in accordance with this rule.$
Magnetic Field due to a Current-carrying Conductor
32 $(a) Name and state the rule which determines the force on a current carrying conductor placed in a uniform magnetic field. (b) Consider the following three diagrams in which the entry of a positive charge (+Q) in a magnetic field is shown. Identify giving reason the case in which the force experienced by the charge is (i) maximum, and (ii) minimum.$
Force on a Current-carrying Conductor
33 $(a) “The third wire of earth connection is very important in domestic electric appliances.” Justify this statement. (b) List two precautions to be taken to avoid the overloading of domestic electric circuits.$
Domestic Electric Circuits
36 (a) $(a) Study the following electric circuit diagram and answer the questions that follow : (i) What does the circuit diagram shows ? (ii) What will happen if the direction of current is reversed ? Justify your answer giving circuit diagram. (b) Name and state the rule to determine the direction of magnetic field associated with a straight current carrying conductor.$
Magnetic Field due to a Current-carrying Conductor
36 (a) $What are magnetic field lines ? How is the direction of magnetic field at a point determined ? Draw the pattern of magnetic field lines of the magnetic field produced by a current carrying circular loop. Mark on it the direction of (i) current and (ii) magnetic field lines. Name the two factors on which the magnitude of the magnetic field due to a current carrying coil depends.$
Magnetic Field due to a Current-carrying Conductor
36 (A) $(i) Draw the pattern of the magnetic field lines for the two parallel straight conductors carrying current of same magnitude ‘I’ in opposite directions as shown. Show the direction of magnetic field at a point O which is equidistant from the two conductors. (Consider that the conductors are inserted normal to the plane of a rectangular cardboard.) (ii) In our houses we receive A.C. electric power of 220 V. In electric iron or electric heater cables having three wires with insulation of three different colours - red, black and green are used to draw current from the mains. (a) What are these three different wires called? Name them colourwise. (b) What is the potential difference between the red wire and the black wire? (c) What is the role of the wire with green insulation in case of accidental leakage of electric current to the metallic body of an electrical appliance?$
Domestic Electric Circuits
36 (a) $The given figure shows the current passing through the straight conductor XY. (i) Copy the diagram and draw the magnetic field lines when current flows from conductor X to Y. (ii) Name and state the rule used in determining the direction of the magnetic field lines in the situation given above. (iii) State Fleming’s left hand rule. Using this rule, determine the direction of force applied on an electron entering a uniform magnetic field as shown in the figure.$
Magnetic Field due to a Current-carrying Conductor
36 (b) $Why can’t two magnetic field lines cross each other ? Draw magnetic field lines showing the direction of the magnetic field due to a current carrying long straight solenoid. State the conclusion which can be drawn from the pattern of magnetic field lines inside the solenoid. Name any two factors on which the magnitude of the magnetic field due to this solenoid depends.$
Magnetic Field due to a Solenoid
36 (b) $(a) Draw the pattern of magnetic field lines of (i) a bar magnet (ii) a current carrying solenoid List two distinguishing features between the two magnetic fields. (b) Study the following three diagrams in which the entry of an electron in a magnetic field is shown. Identify the case in which the magnetic force experienced by the electron is (i) maximum, and (ii) minimum. Give reason for your answers in each case.$
Magnetic Field due to a Solenoid
36 (b) $(i) Define the term solenoid. Draw the pattern of the magnetic field lines in and around a current carrying straight solenoid. Mark on the pattern the (i) direction of current, (ii) direction of field lines near the ends of the solenoid, and (iii) region where the magnetic field is uniform. (ii) How would you make an electromagnet using a current carrying solenoid ?$
Magnetic Field due to a Solenoid
36 (B) $(i) By using the given experimental set-up. How can it be shown that : (a) a force is exerted on the current-carrying conductor AB when it is placed in a magnetic field. (b) the direction of force can be reversed in two ways. (ii) When will the magnitude of the force be highest? (iii) State Fleming’s left hand rule.$
Force on a Current-carrying Conductor
In our homes, we receive the supply of electric power through a main supply also called mains, either supported through overhead electric poles or by underground cables. In our country the potential difference between the two wires (live wire and neutral wire) of this supply is 220 V.
39 (a) $Write the colours of the insulation covers of the line wires through which supply comes to our homes.$
Domestic Electric Circuits
In order to obtain magnetic field lines around a bar magnet, a student performed an experiment using a magnetic compass and a bar magnet. The magnet was placed on a sheet of white paper fixed on a drawing board. Using magnetic needle he obtained on the paper a pattern of magnetic field lines (as shown below) around the bar magnet.
39 (a) $By convention, the field lines emerge from north pole and merge at south pole. Why ? Give reason.$
Magnetic Field and Field Lines
In order to obtain magnetic field lines around a bar magnet, a student performed an experiment using a magnetic compass and a bar magnet. The magnet was placed on a sheet of white paper fixed on a drawing board. Using magnetic needle he obtained on the paper a pattern of magnetic field lines (as shown below) around the bar magnet.
39 (b) $State the relationship between strength of the magnetic field and the degree of closeness of the field lines.$
Magnetic Field and Field Lines
In our homes, we receive the supply of electric power through a main supply also called mains, either supported through overhead electric poles or by underground cables. In our country the potential difference between the two wires (live wire and neutral wire) of this supply is 220 V.
39 (b) $What should be the current rating of the electric circuit (220 V) so that an electric iron of 1 kW power rating can be operated ?$
Domestic Electric Circuits
In our homes, we receive the supply of electric power through a main supply also called mains, either supported through overhead electric poles or by underground cables. In our country the potential difference between the two wires (live wire and neutral wire) of this supply is 220 V.
39 (c) (i) $What is the function of the earth wire ? State the advantage of the earth wire in domestic electric appliances such as electric iron.$
Domestic Electric Circuits
In order to obtain magnetic field lines around a bar magnet, a student performed an experiment using a magnetic compass and a bar magnet. The magnet was placed on a sheet of white paper fixed on a drawing board. Using magnetic needle he obtained on the paper a pattern of magnetic field lines (as shown below) around the bar magnet.
39 (c) (i) $(i) No two field lines can ever intersect each other. Give reason. (ii) The magnetic field in a given region is uniform. Draw a diagram to represent it.$
Magnetic Field and Field Lines
In our homes, we receive the supply of electric power through a main supply also called mains, either supported through overhead electric poles or by underground cables. In our country the potential difference between the two wires (live wire and neutral wire) of this supply is 220 V.
39 (c) (ii) $List two precautions to be taken to avoid electrical accidents. State how these precautions prevent possible damage to the circuit/appliance.$
Domestic Electric Circuits
In order to obtain magnetic field lines around a bar magnet, a student performed an experiment using a magnetic compass and a bar magnet. The magnet was placed on a sheet of white paper fixed on a drawing board. Using magnetic needle he obtained on the paper a pattern of magnetic field lines (as shown below) around the bar magnet.
39 (c) (ii) $Draw the pattern of the magnetic field lines through and around a current carrying solenoid. What does the pattern of field lines inside the solenoid represent ?$
Magnetic Field due to a Solenoid

2024

21 q

14 $The pattern of the magnetic field produced inside a current carrying solenoid is :$
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Magnetic Field due to a Solenoid
14 $The current carrying device which produces a magnetic field similar to that of a bar magnet is :$
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Magnetic Field due to a Solenoid
15 $A rectangular loop ABCD carrying a current I is situated near a straight conductor XY, such that the conductor is parallel to the side AB of the loop and is in the plane of the loop. If a steady current I is established in the conductor as shown, the conductor XY will$
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Force on a Current-carrying Conductor
15 $(\mathrm{e^-})$
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Force on a Current-carrying Conductor
16 $Strength of magnetic field produced by a current carrying solenoid DOES NOT depend upon :$
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Magnetic Field due to a Solenoid
16 $Study the following statements : (a) A fuse in a circuit prevents damage to the circuit due to overloading. (b) Total resistance in a circuit increases due to overloading. (c) During short circuiting the current in the circuit abruptly increases. (d) In order that each appliance has same current, they are connected in parallel to each other. The correct statements are$
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Domestic Electric Circuits
For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
19 $Assertion (A) : Magnetic field lines never intersect each other. Reason (R) : If they intersect, then at the point of intersection, the compass needle would point towards two directions, which is not possible.$
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Magnetic Field and Field Lines
These questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below :
20 $Assertion (A) : The deflection of a compass needle placed near a current carrying wire decreases when the magnitude of an electric current in the wire is increased. Reason (R) : Strength of the magnetic field at a point due to a current carrying conductor increases on increasing the current in the conductor.$
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Magnetic Field due to a Current-carrying Conductor
25 $Draw the pattern of the magnetic field lines due to a straight current carrying conductor indicating the direction of current in the conductor and the direction of the corresponding magnetic field lines.$
Magnetic Field due to a Current-carrying Conductor
25 (a) $Draw a labelled diagram to show the pattern of magnetic field lines produced due to a current carrying straight conductor. Mark on it the direction of current in the conductor and the direction of magnetic field lines.$
Magnetic Field due to a Current-carrying Conductor
25 (b) $Name the device used to magnetise a piece of magnetic material. Draw a labelled diagram to show the arrangement used for the magnetisation of a cylinder made of soft iron.$
Magnetic Field due to a Solenoid
26 $(i) Two magnetic field lines do not intersect each other. Why ? (ii) How is a uniform magnetic field in a given region represented ? Draw a diagram in support of your answer.$
Magnetic Field and Field Lines
32 $(a) How is a solenoid prepared ? Differentiate between a circular coil and a solenoid. (b) Draw the pattern of the magnetic field lines inside a current carrying solenoid. What does this pattern indicate ?$
Magnetic Field due to a Solenoid
32 $Name and state the rule to determine the direction of a : (i) magnetic field produced around a current carrying straight conductor. (ii) force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it.$
Magnetic Field due to a Current-carrying Conductor
32 $“Earth wire is a safety measure in domestic electric circuits.” Justify this statement explaining its role in case of accidental leakage of electric appliances.$
Domestic Electric Circuits
32 $A student fixes a sheet of white paper on a drawing board. He places a bar magnet in the centre of it. He sprinkles some iron filings uniformly around the bar magnet. Then he taps the drawing board gently and observes that the iron filings arrange themselves in a particular pattern. (a) Why do iron filings arrange in a particular pattern ? (b) What does the crowding of iron filings at the ends of the magnet indicate ? (c) What do the lines, along which the iron filings align, represent ? (d) If the student places a cardboard horizontally in a current carrying solenoid and repeats the above activity, in what pattern would the iron filings arrange ? State the conclusion drawn about the magnetic field based on the observed pattern of the lines.$
Magnetic Field and Field Lines
32 $(a) What happens when a bundle of wires of soft iron is placed inside the coil of a solenoid carrying a steady current ? Name the device obtained. Why is it called so ? (b) Draw the magnetic field lines inside a current carrying solenoid. What does this pattern of magnetic field lines indicate ?$
Magnetic Field due to a Solenoid
32 $(a) State Fleming’s left hand rule. Apply this rule to determine the direction of force experienced by a straight current carrying conductor AB placed in a uniform magnetic field as shown. (b) What will happen to an electron which enters in the same field in the same direction in which the current is flowing in the conductor AB ? Give reason to justify your answer.$
Force on a Current-carrying Conductor
32 $Define the term solenoid. Draw the pattern of magnetic field lines around a current carrying solenoid. State how this magnetic field can be used to magnetise a piece of magnetic material, like soft iron.$
Magnetic Field due to a Solenoid
33 $(i) Name two safety measures commonly used in electric circuits and appliances. (ii) The power rating of an electric oven is 220 V; 2 kW. If it is used in a domestic electric circuit of current rating of 5A, what result do you expect ? Justify your answer with necessary calculations.$
Domestic Electric Circuits
32 $Draw a diagram to show the pattern of magnetic field lines on a horizontal sheet of paper due to a straight conductor passing through its centre and carrying current vertically upwards. Mark on it (i) the direction of current in the conductor and (ii) the corresponding magnetic field lines. State right hand thumb rule and check whether the directions marked by you are in accordance with this rule or not.$
Magnetic Field due to a Current-carrying Conductor

2023

27 q

14 $The correct pattern of magnetic field lines of the field produced by a current carrying circular loop is :$
Tap an option to check your answer.
Magnetic Field due to a Current-carrying Conductor
14 $In domestic electric circuits the wiring with 15 A current rating is for the electric devices which have$
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Domestic Electric Circuits
14 $A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in the figure. The direction of the magnetic field will be north to south at a point :$
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Magnetic Field due to a Current-carrying Conductor
15 $The magnetic field inside a long straight current carrying solenoid :$
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Magnetic Field due to a Solenoid
15 $An alpha particle enters a uniform magnetic field as shown. The direction of motion of the alpha particle is :$
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Force on a Current-carrying Conductor
16 $An alpha particle enters a uniform magnetic field as shown. The direction of force experienced by the alpha particle is :$
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Force on a Current-carrying Conductor
16 $A positron enters a uniform magnetic field at right angles to it as shown. The direction of force experienced by the positron will be :$
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Force on a Current-carrying Conductor
16 $For a current in a long straight solenoid, N and S poles are created at the two ends. Among the following statements, the incorrect statement is :$
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Magnetic Field due to a Solenoid
16 $The resultant magnetic field at point ‘P’ situated midway between two parallel wires (placed horizontally) each carrying a steady current I is$
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Magnetic Field due to a Current-carrying Conductor
For questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below :
19 $Assertion (A) : The magnetic field lines around a current carrying straight wire do not intersect each other. Reason (R) : The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.$
Tap an option to check your answer.
Magnetic Field and Field Lines
Q. Nos. 17 to 20 are Assertion – Reason based questions. These consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below :
20 $Assertion (A) : The strength of the magnetic field produced at the centre of a current carrying circular coil increases on increasing the number of turns in it. Reason (R) : The current in each circular turn has the same direction and the magnetic field due to each turn then just adds up.$
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Magnetic Field due to a Current-carrying Conductor
For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
20 $Assertion (A) : Magnetic field lines do not intersect each other. Reason (R) : Magnetic field lines are imaginary lines, the tangent to which at any point gives the direction of the field at that point.$
Tap an option to check your answer.
Magnetic Field and Field Lines
For questions number 17 to 20, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below :
20 $Assertion (A) : Two magnetic field lines around a current carrying straight wire do not intersect each other. Reason (R) : The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.$
Tap an option to check your answer.
Magnetic Field and Field Lines
Q. No. 17 to 20 are Assertion – Reasoning based questions. These consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below.
20 $Assertion (A) : A current carrying straight conductor experiences a force when placed perpendicular to the direction of magnetic field. Reason (R) : The net charge on a current carrying conductor is always zero.$
Tap an option to check your answer.
Force on a Current-carrying Conductor
25 $Consider a circular loop of thick copper wire lying horizontally on a table. Let the current pass through the loop anticlockwise. Draw the magnetic field lines to show the direction and the pattern of the magnetic field inside and outside the loop.$
Magnetic Field due to a Current-carrying Conductor
26 $Draw magnetic field lines produced around a straight current carrying conductor passing through a cardboard. How will the strength of the magnetic field change when the point where magnetic field is to be determined is moved away from the conductor ?$
Magnetic Field due to a Current-carrying Conductor
26 $State the rule to determine the direction of a (a) magnetic field produced around a straight conductor carrying current and (b) force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it.$
Magnetic Field due to a Current-carrying Conductor
32 (a) $(i) A straight cylindrical conductor is suspended with its axis perpendicular to the magnetic field of a horse-shoe magnet. The conductor gets displaced towards left when a current is passed through it. What will happen to the displacement of the conductor if the (1) current through it is increased ? (2) horse-shoe magnet is replaced by another stronger horse-shoe magnet ? (3) direction of current through it is reversed ? (ii) Name and state the rule for determining the direction of force on a current carrying conductor in a magnetic field.$
Force on a Current-carrying Conductor
32 $What is a solenoid ? Draw a diagram to show the pattern of magnetic field around a current carrying solenoid. Name the region of uniform magnetic field.$
Magnetic Field due to a Solenoid
32 $Explain the meaning of overloading of an electrical circuit. List two possible causes due to which overloading may occur in household circuits. Write one preventive measure that should be taken to avoid overloading of domestic circuits.$
Domestic Electric Circuits
32 $(a) List two factors on which the magnitude of magnetic field produced by a current carrying straight conductor depends. (b) State the rule which determines the direction of magnetic field in the above case. (c) Draw the pattern of magnetic field lines produced in this case.$
Magnetic Field due to a Current-carrying Conductor
32 $What is a solenoid ? When does a solenoid behave as a magnet ? Draw the pattern of the magnetic field produced inside it showing the directions of the magnetic field lines.$
Magnetic Field due to a Solenoid
32 (a) $(i) State the rule used to find the force acting on a current carrying conductor placed in a magnetic field. (ii) Given below are three diagrams showing entry of an electron in a magnetic field. Identify the case in which the force will be (1) maximum and (2) minimum respectively. Give reason for your answer.$
Force on a Current-carrying Conductor
32 (b) $Draw the pattern of the magnetic field produced around a vertical current carrying straight conductor passing through a horizontal cardboard. Mark the direction of current and the magnetic field lines. Name and state the rule which is used to determine the direction of magnetic field associated with a current carrying conductor.$
Magnetic Field due to a Current-carrying Conductor
32 (A) $(i) Why is an alternating current (A.C.) considered to be advantageous over direct current (D.C.) for the long distance transmission of electric power ? (ii) How is the type of current used in household supply different from the one given by a battery of dry cells ? (iii) How does an electric fuse prevent the electric circuit and the appliances from a possible damage due to short circuiting or overloading.$
Domestic Electric Circuits
32 (b) $(i) Draw the pattern of magnetic field lines of (1) a current carrying solenoid (2) a bar magnet (ii) List two distinguishing features between the two fields.$
Magnetic Field due to a Solenoid
32 (B) $For the current carrying solenoid as shown, draw magnetic field lines and give reason to explain that out of the three points A, B and C, at which point the field strength is maximum and at which point it is minimum ?$
Magnetic Field due to a Solenoid

2022

21 q

2 $As shown in the diagram an aluminium rod ‘AB’ is suspended horizontally between the two poles of a strong horse shoe magent in such a way that the axis of rod is horizontal and the direction of the magnetic field is vertically upward. The rod is connected in series with a battery and a key. State giving reason : (a) What is observed when a current is passed through the aluminum rod from end B to end A ? (b) What change is observed in a situation in which the axis of the rod ‘AB’ is moved and aligned parallel to the magnetic field and current is passed in the rod in the same direction ?$
Force on a Current-carrying Conductor
2 OR $“Magnetic field is a physical quantity that has both direction and magnitude.” How can this statement be proved with the help of magnetic field lines of a bar magnet ?$
Magnetic Field and Field Lines
6 (a) $(a) Name the poles P, Q, R and S of the magnets in the following figures ‘a’ and ‘b’ : (b) State the inference drawn about the direction of the magnetic field lines on the basis of these diagrams.$
Magnetic Field and Field Lines
6 (a) $(i) Name and state the rule to determine the direction of force experienced by a current carrying straight conductor placed in a uniform magnetic field which is perpendicular to it. (ii) An alpha particle while passing through a magnetic field gets projected towards north. In which direction will an electron project when it passes through the same magnetic field ?$
Force on a Current-carrying Conductor
6 (b) $When is the force experienced by a current - carrying straight conductor placed in a uniform magnetic field. (i) Maximum ; (ii) Minimum ?$
Force on a Current-carrying Conductor
6 (b) $(i) What is a solenoid ? (ii) Draw the pattern of magnetic field lines of the magnetic field produced by a solenoid through which a steady current flows.$
Magnetic Field due to a Solenoid
11 $What is a Solenoid ? Draw the pattern of the magnetic field lines around a current carrying solenoid. Mark on the pattern the region where the magnetic field is uniform.$
Magnetic Field due to a Solenoid
12 (a) $In the diagram given below, Coil - 1 is connected in series with a battery and a plug key while Coil - 2 is connected with a galvanometer. (i) Why does the galvanometer show deflection only when the key (K) is plugged in and not when a steady current starts flowing in the circuit ? (ii) What is observed in the galvanometer, when the key is plugged out ? (iii) State the conclusion based on the observation of this activity.$
Magnetic Field due to a Solenoid
12 (b) $In the figure given below, a simple electric motor is shown : As shown in the figure, the current in the coil ABCD flows from A to B in the arm AB and C to D in the arm CD. (i) State the directions in which the arms AB and CD will experience a force. (ii) Identify the part of the electric motor that reverses the flow of current in the coil ABCD and write its name. (iii) After the reversal of flow of current in the coil ABCD, state the directions in which the arms AB and CD will experience a force. (iv) Name the rule which is applied to determine the direction of force on a current carrying conductor placed in a magnetic field.$
Force on a Current-carrying Conductor
AB is a coil of copper wire having a large number of turns. The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards the end B of the coil, a deflection is observed in the galvanometer.
14 (a) $State the reason for using galvanometer in the activity and why does its needle deflects momentarily when magnet is moved towards the coil.$
Force on a Current-carrying Conductor
AB is a coil of copper wire having a large number of turns. The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards the end B of the coil, a deflection is observed in the galvanometer.
14 (b) $What would be observed in the galvanometer in a situation when the coil and the bar magnet both move with the same speed in the same direction ? Justify your answer.$
Force on a Current-carrying Conductor
AB is a coil of copper wire having a large number of turns. The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards the end B of the coil, a deflection is observed in the galvanometer.
14 (c) $State the conclusion that can be drawn from this activity. Will there be any change in the momentary deflection in the galvanometer if number of turns in the coil is increased and a more stronger magnet is moved towards the coil ?$
Force on a Current-carrying Conductor
AB is a coil of copper wire having a large number of turns. The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards the end B of the coil, a deflection is observed in the galvanometer.
14 (c) OR $What is electromagnetic induction ? What is observed in the galvanometer when a strong bar magnet is held stationary near one end of a coil of large number of turns ? Justify your answer.$
Force on a Current-carrying Conductor
A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminum rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions :
15 (a) $Why does the rod get displaced on passing current through it ?$
Force on a Current-carrying Conductor
A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.
15 (a) $Draw a diagram to show this pattern of iron filings.$
Magnetic Field and Field Lines
A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminum rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions :
15 (b) $State the rule that determines the direction of the force on the conductor AB.$
Force on a Current-carrying Conductor
A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.
15 (b) $Draw the magnetic field lines of a bar magnet showing the poles of the bar magnet as well as the direction of the magnetic field lines.$
Magnetic Field and Field Lines
A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.
15 (c) (i) $How is the direction of magnetic field at a point determined using the field lines ? Why do two magnetic field lines not cross each other ?$
Magnetic Field and Field Lines
A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminum rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions :
15 (c) $(i) If the U shaped magnet is held vertically and the aluminum rod is suspended horizontally with its end B towards due north, then on passing current through the rod from B to A as shown, in which direction will the rod be displaced ? (ii) Name any two devices that use current carrying conductors and magnetic field.$
Force on a Current-carrying Conductor
A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.
15 (c) (ii) $How are the magnetic field lines of a bar magnet drawn using a small compass needle ? Draw one magnetic field line each on both sides of the magnet.$
Magnetic Field and Field Lines
A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminum rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions :
15 (c) OR $Draw the pattern of magnetic field lines produced around a current carrying straight conductor held vertically on a horizontal cardboard. Indicate the direction of the field lines as well as the direction of current flowing through the conductor.$
Magnetic Field due to a Current-carrying Conductor

The 10 board questions to practise first

The questions and kinds of question the board asked most often come first. Each one says how often and when.

Question 1
Asked 5 times: 2022*, 2023*, 2024*, 2025*, 2026 (* = numbers or wording changed that year) See all 5 times it was asked
39 (a) $(i) What is a solenoid ? Draw a diagram showing the magnetic field pattern due to a current-carrying solenoid (inside and outside). (ii) Name any two factors on which the magnitude of the magnetic field due to a current-carrying solenoid depends. (iii) A current-carrying solenoid is stretched and converted into a straight wire carrying current. Draw a diagram showing the magnetic field pattern around it and mark the direction of the magnetic field.$
Question 2
This type asked 5 times: 2022, 2023, 2024, 2025, 2026. This one: 2026 See all 5 of this type
39 (B) $(i) Draw a diagram, showing the magnetic field lines in and around the current carrying solenoid. Write any two salient features of these lines. (ii) What is an electromagnet and how is it made ?$
Question 3
This type asked 5 times: 2022, 2023, 2024, 2025, 2026. This one: 2026 See all 5 of this type
39 (A) $(i) Draw a diagram showing the magnetic field lines around a bar magnet. Write any two characteristics of magnetic field lines. (ii) Write the statement of Right hand thumb rule. (iii) The concentric circles representing the magnetic field around a current carrying straight wire become larger and larger as we move away from the wire. How does magnetic field change on these concentric circles ?$
Question 4
Asked 4 times: 2023*, 2024*, 2025*, 2026 (* = numbers or wording changed that year) See all 4 times it was asked
39 (b) $(i) With the help of a diagram, describe an activity in brief to show that a current-carrying straight conductor produces a magnetic field around it. (ii) Two straight current-carrying conductors (A) and (B) are shown in the figures below : (I) Mark the direction of the magnetic fields around these current-carrying conductors (A) and (B). (II) Compare the strengths of magnetic fields produced (1) at points P and Q and (2) at points Q and R due to these current-carrying conductors, qualitatively.$
Question 5
Asked 4 times: 2022*, 2023*, 2025*, 2026 (* = numbers or wording changed that year) See all 4 times it was asked
37 $On the basis of the given circuit arrangement, answer the following questions : (a) What happens to the rod AB when the key K is closed and why ? (b) Name and state the rule that determines this behaviour of the rod AB in the above situation.$
Question 6
This type asked 4 times: 2023, 2024, 2025, 2026. This one: 2026 See all 4 of this type
39 (b) $B$
Question 7
This type asked 4 times: 2022, 2023, 2024, 2026. This one: 2026 See all 4 of this type
Two statements are given, one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the options given below.
32 $Assertion (A) : Direction of force exerted on a current-carrying conductor placed in a magnetic field remains same if the directions of both magnetic field and current flowing through the conductor are reversed. Reason (R) : The direction of force exerted on a current-carrying conductor placed in an external magnetic field can be determined by using magnetic compass.$
Tap an option to check your answer.
Question 8
Asked 3 times: 2023*, 2024*, 2026 (* = numbers or wording changed that year) See all 3 times it was asked
39 (a) $(i) State the rules to determine the following : (I) Direction of magnetic field produced around a current-carrying straight conductor. (II) Direction of force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it. (ii) (I) Draw the magnetic field lines due to a current-carrying solenoid. (II) Three points A, B and C are marked in the above given diagram of the current-carrying solenoid. Out of the three points A, B and C, at which point is the magnetic field strength maximum and at which point is it minimum ?$
Question 9
Asked 3 times: 2023*, 2025*, 2026 (* = numbers or wording changed that year) See all 3 times it was asked
39 (b) $(i) Draw the pattern of magnetic field lines through and around a current-carrying circular loop. (ii) State the rule to find out the direction of the magnetic field inside and around the circular loop. (iii) Give reasons : (I) Why should a burnt-out fuse be replaced by another fuse of identical rating only, in an electric circuit ? (II) Why is soft iron-core used in making an electromagnet ?$
Question 10
Asked 3 times: 2024*, 2025*, 2026 (* = numbers or wording changed that year) See all 3 times it was asked
39 (b) $(i) Draw a schematic diagram of a domestic electric circuit which includes the following devices : (I) A fuse (II) A power meter (III) One light point (IV) A power plug (ii) Why is it necessary to connect an earth wire to the electrical appliances having metallic covers ?$

Quick revision

5 most-asked questions · 13 key points · 6 diagrams

Checked against NCERT Science (CBSE Class 10), Chapter 12.

Most asked in board papers

1
Force on a current-carrying conductor: activity with a rod in a magnet, Fleming's left-hand rule, when the force is largest, deflection of alpha particles
Asked 5 times: 2026, 2025, 2024, 2023, 2022
2
Field of a straight wire and a circular loop: pattern of field lines, right-hand thumb rule, what the strength depends on
Asked 5 times: 2026, 2025, 2024, 2023, 2022
3
Magnetic field lines: draw them for a bar magnet, properties, why two lines never cross, how closeness shows strength
Asked 5 times: 2026, 2025, 2024, 2023, 2022 · 1 mark
4
Solenoid and electromagnet: field pattern like a bar magnet, uniform field inside, factors for its strength
Asked 5 times: 2026, 2025, 2024, 2023, 2022
5
Domestic circuits and safety: live, neutral and earth wires, earthing, fuse, short-circuiting and overloading, 5 A and 15 A circuits
Asked 4 times: 2026, 2025, 2024, 2023

Must-know points

Oersted's observation: A compass needle placed near a current-carrying wire is deflected; reversing the current reverses the deflection. Oersted showed that electricity and magnetism are related: a current produces a magnetic field.
Magnetic field lines: The region round a magnet in which its force can be detected is its magnetic field; it has both direction and magnitude. Field lines are traced with a compass. By convention they emerge from the north pole and merge at the south pole outside the magnet, and go from south to north inside it: they are closed curves.
Properties of field lines: No two field lines cross: if they did, the compass needle would point two ways at one point, which is impossible. The field is stronger where the lines are crowded (near the poles). The direction of the field at a point is the tangent to the line there. Parallel, equally spaced lines show a uniform field.
Field of a straight conductor: The field lines are concentric circles centred on the wire, in a plane perpendicular to it. The field is stronger for a larger current and weaker farther from the wire (it depends inversely on the distance). Reversing the current reverses the direction.
Right-hand thumb rule: Hold a current-carrying straight conductor in your right hand with the thumb pointing in the direction of current; the fingers wrapped around it show the direction of the magnetic field lines.
Field of a circular loop: Near the wire the lines are circles; at the centre of the loop they become nearly straight, and every part of the loop adds to the field in the same direction. For a coil of n turns the field is n times that of one turn. It is stronger for a larger current and more turns.
Solenoid: A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder. Its field pattern is like that of a bar magnet: one end acts as a north pole, the other as a south pole. Inside, the field lines are parallel straight lines: the field is uniform.
Electromagnet: The strong field inside a current-carrying solenoid magnetises a soft iron core placed in it: an electromagnet. It is stronger with more turns, a larger current and a soft iron core, and stops being a magnet when the current is switched off.
Force on a current-carrying conductor: A current-carrying rod in a magnetic field is pushed sideways: a force acts on it. The force is largest when the current is perpendicular to the field, and zero when parallel. Reversing the current, or the field, reverses the force. A moving charge feels the same force (an alpha particle is a positive charge, an electron negative).
Fleming's left-hand rule: Stretch the thumb, forefinger and middle finger of the left hand so they are mutually perpendicular. If the forefinger points in the direction of the magnetic field and the middle finger in the direction of current, the thumb points in the direction of motion or the force on the conductor.
Domestic electric circuits: Supply comes by the live wire (red insulation) and the neutral wire (black); in India the potential difference between them is 220 V. It passes through a main fuse and the electricity meter. Two circuits: 15 A for geysers and air coolers, 5 A for bulbs and fans. Appliances are joined in parallel, each with its own switch.
Earth wire: The earth wire (green insulation) is connected to a metal plate deep in the earth. The metallic body of an appliance (iron, toaster, refrigerator) is joined to it, giving a low-resistance path, so any leakage current keeps the body at earth's potential and the user does not get a severe shock.
Fuse, short-circuiting and overloading: Short-circuiting: the live and neutral wires come into direct contact (damaged insulation, a fault in an appliance), so the current rises sharply. Overloading: too many appliances on one socket, or an accidental hike in supply voltage. The fuse melts and stops the unduly high current, protecting the circuit and appliances.

Diagrams to practise

Field lines around a bar magnet (Figure 12.4): label N and S poles · lines from N to S outside · arrows on every line · lines crowded near the poles, never crossing
Field lines around a straight conductor (Figure 12.6): label wire through a cardboard · concentric circles · direction by right-hand thumb rule · circles farther apart away from the wire
Field lines of a circular loop (Figure 12.8): label current direction in the loop · circles near each side of the wire · nearly straight lines at the centre · arrows in opposite senses at the two sides
Field lines of a solenoid (Figure 12.10): label turns of the coil and current direction · parallel lines inside (uniform field) · N and S ends · lines outside like a bar magnet
Fleming's left-hand rule (Figure 12.13): label forefinger: magnetic field · middle finger: current · thumb: force (motion) · all three mutually perpendicular
A domestic electric circuit (Figure 12.15): label live, neutral and earth wires · electricity meter and main fuse · distribution box · appliances in parallel, each with a switch

Mistakes that cost marks

Using the right hand for the force

Right-hand thumb rule: direction of the magnetic field around a current. Fleming's left-hand rule: direction of the force on a current in a field.

Field lines drawn wrong

Every line needs an arrow: N to S outside a magnet, S to N inside. Lines never cross and never start or end in mid-air. For a straight wire draw circles, closer together near the wire.

Wrong direction of current for a moving charge

For an alpha particle or a positron, the current is in its direction of motion. For an electron, the current is opposite to its motion. Then apply Fleming's left-hand rule.

Earth wire and fuse confused

The earth wire protects the user from a shock through a metal body. The fuse protects the circuit and appliances from too large a current. A fuse goes in series in the live wire.

What the solenoid's strength depends on

It depends on the number of turns, the current and the core material (soft iron). It does not depend on the direction of the current, which only changes which end is N.

12.1 Magnetic Field and Field Lines

Question

12.2.2 Right-Hand Thumb Rule

Solved Examples

Questions

12.2.4 Magnetic Field due to a Current in a Solenoid

Questions

12.3 Force on a Current-Carrying Conductor in a Magnetic Field

Solved Examples

Questions

12.4 Domestic Electric Circuits

Questions

Exercises

What the board has asked from this chapter

2026

2025

2024

2023

2022

The 10 board questions to practise first

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Most asked in board papers

Must-know points

Diagrams to practise

Mistakes that cost marks