Physics-DPP-2-Magnetism

PHYSICS Topic: Magnetism Date: 1. A flat circular coil of n turns and radius r carries a current i. Its magnetic moment is: (a) r2 ni (b) 2rni (c) μ æç ni ö÷ (d)  r2ni 0 çè 2πr ø÷ 0 2. A long straight conductor carrying a current lies along the axis of a ring. The conductor will exert a force on the ring if the ring. (a) carries a current (b) has uniformly distributed charge (c) has nonuniformly distributed charge (d) none of the above 3. Two straight infinitely long current carrying wires are kept along 2-axis at the co-ordinates [0, a, 0] & [0, – a, 0] respectively as shown in figure. The current in each wire is equal & along negative z-axis (into the lane of the paper]. The variation of magnetic field on the x-axis will be approximately. (a) (c) (d) 4. A conductor ABCDEF, with each side of length L, is bent as shown. It is carrying a current I in a uniform magnetic induction (field) B, parallel to the positive y-direction. The force experienced by the wire is (a) BIL in the positive y-direction (b) BIL in the negative z-direction (c) 3BIL (d) zero 5. A horizontal straight conductor of mass m and length l is placed in a uniform verticle magnetic field of magnitude B. An amount of charge Q passes through the rod in a very short time such that the conductor begins to move only after all the charge has passed through it. Its initial velocity will be (a) BQlm (b) BQ lm (c) BQl Bl m (d) mQ PHYSICS Topic: Magnetism Date: 6. A conductor AB of length l, carrying a current i, is placed perpendicular to a long straight conductor XY carrying a current I, as shown. The force on AB will act (a) upward (b) downward (c) to the right (d) to the left 7. In the previous question, the force on AB has magnitude (a) 8. μ0 Ii In2 2π (b) (b) μ0 Ii In3 2π (c) (c) 3μ0 Ii 2π (d) (d) 2 μ0 Ii 3π A square loop ABCD, carrying a current i, is placed near and coplanar with a long straight conductor XY carrying a current I. (a) There is no net force on the loop. (b) The loop will be attracted by the conductor only if the current in the loop flows clockwise. (c) The loop will be attracted by the conductor only if the current in the loop flows anticlockwise. (d) The loop will always be attracted by the conductor. 9. A flat coil of n turns, area A and carrying a current i is placed in a uniform magnetic field of magnitude B. The plane of the coil makes an angle  with the direction of the field. The torque acting on the coil is nAi (a) BinAsin (b) B sin θ (c) BinAcos  (d) Bin2 Acos 10. The square loop ABCD, carrying a current I, is placed in a uniform magnetic field B, as shown. The loop can rotate about the axis XX. The plane of the loop makes an angle  ( < 90º) with the direction of B. Through what angle will the loop rotate by itself before the torque on it becomes zero? (a)  (b) 90º –  (c) 90º +  (d) 180º –  PHYSICS Topic: Magnetism Answer Key Date: 1. (a) 2. (d) 3. (d) 4. (b) 5. (c) 6. (a) 7. (b) 8. (b) 9. (c) 10. (c)