Physics Times – July 2019

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   A wire along x-axis carries a current 3.5A. The force
   on a 1 cm section of the wire exerted by the magnetic
   field

   
   


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Magnetism & Matter
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Electro Magnetic Induction

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B0.74T jˆ0.36T kˆ

(a) 2.59kˆ1.26 10ˆj ^2 N

(b) 1.26kˆ2.59 10ˆj ^2 N

(c) 1.26kˆ2.59 10ˆj ^2 N

(d) 2.59 1.26 10kˆ ˆj ^2 N

Magnetism & Matter

6. A bar magnet of moment M is bent into arc, its
   moment now
   (a) Decreases (b) Increases
   (c) Does not change (d) May change


7. A very long magnet is held vertically with its south
   pole on a table. A single neutral point is located on
   the table to the
   (a)East of the magnet (b) North of the magnet
   (c)West of the magnet (d) South of the magnet


8. The coil in a MCG has an area of 4 cm^2 and 500

turns. The intensity of magnetic induction is 2 T.

When a current of 10 ^4 A is passed through it, the

deflection is 20 . The couple per unit twist is (N-

m/degree)

(a) 2 10 ^6 (b) 3 10 ^6 (c) 5 10 ^6 (d) 4 10 ^6

9. Due to the earth’s magnetic field, charged cosmic
   ray particles
   (a) Can never reach the equator
   (b) Can never reach the poles
   (c) Require less kinetic energy to reach the equator
   than the poles
   (d) Require greater kinetic energy to reach the
   equator than the poles
   10.A magnet is placed on a paper in a horizontal plane
   for locating neutral points. A dip needle placed at
   the neutral point will be horizontal at the
   (a) Magnetic equator (b) Magnetic pole
   (c) Latitude angle of 60  (d) Latitude angle 45 

Electro Magnetic Induction

11.A coil of 40  resistance has 100 turns and radius

6 mm is connected to an ammeter of resistance of

160 . Coil is placed perpendicular to the magnetic

field. When coil is taken out of the field, 32 C

charge flows through it. The intensity of magnetic

field will be

(a) 5.66 T (b) 6.55 T

(c) 0.566 T (d) 0.655 T

12.An electromagnetic wave going through vacuum

is described byE E kx t 0 sin( );

B B kx t 0 sin( ). Which of the following is

true?

(a) E k B 0  0  (b) E B k 0  0

(c) E k B 0  2 0  (d) E B k0 0

13.An electric field of 300V/m is confined to a circular

area 10 cm in diameter. If the field is increasing at

the rate of 20V/m-s, the magnitude of magnetic field

at a point 15cm from the center of the circle will be-

(a) 1.85 10 T ^17 (b) 1.85 10 T ^15

(c) 1.85 10 T ^16 (d) 1.85 10 T ^18

14.A magnet is dropped down inside a long vertical

copper tube

(a) The magnet moves with continuously

increasing velocity and ultimately acquires a

constant terminal velocity

(b) The magnet moves with continuously

decreasing velocity and ultimately comes to

rest

(c) The magnet moves with continuously

increasing velocity but constant acceleration

(d) The magnet moves with continuously

increasing velocity and acceleration

15.Which of the following is constructed on the

principle of electromagnetic induction?

(a) Voltmeter (b) Galvanometer

(c) Generator (d) Electric motor

Magnetic Effects of Current

1. a 2. d 3. d 4. d 5. a

Magnetism & Matter

6. a 7. b 8. a 9. a 10. a

Electro Magnetic Induction

11. c 12. a 13. d 14. a 15. c

Magnetic Effects of Current

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Magnetism & Matter

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Electro Magnetic Induction

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