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Science · Textbook solutions

Magnetic Effects of Electric Current

Every solved example, exercise, and miscellaneous question — in the order the textbook teaches them. · 25 questions

12.1 Magnetic Field and Field Lines

1 q

Question

Practice · 1
  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
  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
  1. IT 12.2 Q1
    Draw magnetic field lines around a bar magnet.
  2. IT 12.2 Q2
    List the properties of magnetic field lines.
  3. 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
  1. 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.
  2. IT 12.3 Q2
    The magnetic field in a given region is uniform. Draw a diagram to represent it.
  3. Choose the correct option.
    IT 12.3 Q3
    The magnetic field inside a long straight solenoid-carrying current
    1. A.
      is zero.
    2. B.
      decreases as we move towards its end.
    3. C.
      increases as we move towards its end.
    4. D.
      is the same at all points.

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

4 q

Solved Examples

Worked · 1
  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
  1. 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
  2. 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?
  3. 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
    1. A.
      towards south
    2. B.
      towards east
    3. C.
      downward
    4. D.
      upward

12.4 Domestic Electric Circuits

3 q

Questions

Practice · 3
  1. IT 12.5 Q1
    Name two safety measures commonly used in electric circuits and appliances.
  2. 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.
  3. IT 12.5 Q3
    What precaution should be taken to avoid the overloading of domestic electric circuits?

Exercises

10 q
  1. Ex 12 Q1
    Which of the following correctly describes the magnetic field near a long straight wire?
    1. A.
      The field consists of straight lines perpendicular to the wire.
    2. B.
      The field consists of straight lines parallel to the wire.
    3. C.
      The field consists of radial lines originating from the wire.
    4. D.
      The field consists of concentric circles centred on the wire.
  2. Ex 12 Q2
    At the time of short circuit, the current in the circuit
    1. A.
      reduces substantially.
    2. B.
      does not change.
    3. C.
      increases heavily.
    4. D.
      vary continuously.
  3. 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.
  4. Ex 12 Q3 (b)
    A wire with a green insulation is usually the live wire of an electric supply.
  5. Ex 12 Q4
    List two methods of producing magnetic fields.
  6. Ex 12 Q5
    When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
  7. 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?
  8. 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.
  9. Ex 12 Q8
    When does an electric short circuit occur?
  10. Ex 12 Q9
    What is the function of an earth wire? Why is it necessary to earth metallic appliances?