Physics-DPP-1-2.Magnetism

PHYSICS Topic: Magnetism Date: 1. ABCD is a square loop made of a uniform conducting wire. A current enters the loop at A and leaves at D. The magnetic field is (a) zero only at the centre of the loop (b) maximum at the centre of loop (c) zero at all points outside the loop (d) zero at all points inside the loop 2. Two long thin wires ABC and DEF are arranged as shown. They carry currents I as shown. The magnitude of the magnetic field at O is (a) zero (b) μ0 I 4πa (c) μ0 I 2πa (d) μ0I 3. An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude (a) zero (b) μ0 ne 2πr (c) μ0ne 2r (d) μ n2e 2r 4. Current flows through a straight, thin-walled tube of radius r. The magnetic field at a distance x from the axis of the tube has magnitude B. (a) B  x, for 0 < x < r (b) B  1/x, for 0 < x < r (c) B = 0, for 0  x < r (d) B = 0, only for x = 0 5. A coaxial cable consists of a thin inner conductor fixed along the axis of a hollow outer conductor. The two conductors carry equal currents in opposite directions. Let B1 and B2 be the magnetic fields in the regions between the conductors, and outside the conductor, respectively. (a) B1  0, B2  0 (b) B1 = B2 = 0 (c) B1  0, B2 = 0 (d) B1 = 0, B2  0 6. In the pervious question, if both conductors carry equal currents in the same direction, (a) B1  0, B2  0 (b) B1 = B2 = 0 (c) B1  0, B2 = 0 (d) B1 = 0, B2  0 PHYSICS Topic: Magnetism Date: 7. A wire carry a current I is shaped as shown. Section AB is a quarter circle of radius r. The magnetic field at C is directed. (a) along the bisector of the angle ACB, away from AB (b) along the bisector of the angle ACB, towards AB (c) Perpendicular to the plane of the paper, directed into the paper. (d) At an angle /4 to the plane of the paper. 8. Two parallel beams of protons and electrons, carrying equal currents, are fixed at a separation d. The protons and electrons move in opposite directions. P is a point on a line joining the beams, at a distance x from any one beam. The magnetic field at P is B. If B is plotted against x, which of the following best represents the resulting curve? (a) (b) (c) (d) 9. If E and B denote electric and magnetic fields respectively, which of the following is diamensionless? E æE ö2 E μ (a) (b) μ0 ε0 (c) μ0 ε0 ç ÷ (d) ´ 0 B çèBø÷ ε0 B 10. The wire loop formed by joining two semicircular sections of radii R1 and R2, and centre C, carries a current I, as shown. The magnetic field at C has magnitude μ0 I æç 1 1 ö÷ μ0 I æç 1 1 ö÷ μ0 I æç 1 1 ö÷ μ0 I æç 1 1 ö÷ (a) 2 ççèR + R2 ø÷ (b) 4 çèR1 + R ø÷ (c) 2 çèR1 - R ø÷ (d) 4 çèR1 - R ø÷ PHYSICS Topic: Magnetism Answer key Date: 1.(a) 2.(c) 3. (c) 4. (c) 5. (c) 6. (a) 7. (c) 8. (c) 9. (a) 10. (d)

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