Physics-Magnetic Field

Test Preparation on Physics - Magnetic Field

1.

The strength of the magnetic field around a straight wire :

1is directly proportional to the square of the distance
2obeys inverse square law
3is same everywhere around the wire from the wire
4none of these

2.

A magnetic needle is kept in non-uniform magnetic field.It experiences:

1a force and torque
2a force but not a torque
3a torque but not a force
4neither a force nor a torque

3.

A long wire carries a current of 20 A along the axis of a solenoid, the field due to the solenoid is 4 mT. The resultant field at a point 3 mm from the solenoid axis is :

11.33 mT
24.2 mT
32.1 mT
48.4 mT

Bwire=m0

4.

A circular current-carrying coil has a radius R. The distance from the center of the coil on the axis where the magnetic induction will be -^th of its value at the centre8of the coil, is :

1R?3
2R/?3
32R/?3
4(2?3)R

Magnetic field on the axis of a circular coil having n turns is B = m0/4p 2pniR2/(R2+x2)3/2 1/8 m0/4p 2pni/R = m0/4p 2pniR2/(R2+x2)3/2

5.

Through two parallel wires P and Q, 10 A and 2 A ofcurrents are passed respectively in opposite directions.' Ifthe wire P is infinitely long and the length of the wireQ is 2 cm, the force on the conductor Q which is situatedat 10 cm distance from P, will be:

18 x 10-5 N
23 x 10-7 N
34 x 10-5 N
44 x 10-7 N

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