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Force on a current-carrying conductor and motors

This type of question, asked 4 times: 2022, 2023, 2024, 2026. All 7 questions below, oldest first.

Try each one first, then open its answer.

  1. Question 1 (case study, 4 parts)

    2022

    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 ?
    15 (b)
    State the rule that determines the direction of the force on the conductor AB.
    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.
    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.

  2. Question 2

    2023

    Two statements are given, one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the options 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.

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  3. Question 3

    2024

    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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  4. Question 4

    2026

    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.

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  5. Question 5

    2026

    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.

  6. Question 6

    2026

    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.

  7. Question 7

    2026

    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 ?