Moving Charges and Magnetism

A circular coil of radius 10 cm is placed in X - Y plane, a constant current of 10 A is flowing in it in clockwise sense. The magnitude and direction of magnetic field at the centre are

• 2 $\pi$ $\times$ 10^-5 T along z - axis

• 2 $\pi$ $\times$ 10^-5 T along $-$ z axis

• 2 $\times$ 10^-5 T along z - axis

• 2 $\times$ 10^-5 T along $-$ z axis

A constant current I is flowing in a long solid cylindrical rod of radius R. The ratio of magnetic fields at the perpendicular distances R/2 and 3R/2 from the axis of the wire:

• 3:1

• 1:3

• 3:4

• 4:3

A constant current 10 A is flowing in a long conducting wire, the magnitude of the magnetic field due to the wire at a distance 100 m along the axis of the wire is

• 0

• 4 $\pi\times$ 10^-8 T

• 2 $\pi\times$ 10^-8 T

• 2 $\times$ 10^-8 T

A wire is kept along north - south direction and a constant current is flowing in it in north to south direction. What will be the direction of the force on the wire if it is placed in constant magnetic field along west to east direction:

• Downwards

• Upwards

• Along left side

• Along right side

Out of miliammeter and an ammeter the -------- is of lesser resistance.

The resistance of an ideal voltmeter should be ----

The direction of torque on the coil is along ------ axis.

• X - axis

• Negative X - axis

• Y - axis

• Negative Y - axis

The material used in making of the suspension wire used in moving coil galvanometer should be of -------torsional constant and ------- elastic constant.

• high, low

• high, high

• low, low

• low, high

A charge particle is moving undeflected in a uniform electric and magnetic fields, now the magnetic field is switched off, the trajectory of the particle will be

• circular

• helical

• straight line

• elliptical

The frequency of a charge particle revolving in a perpendicular uniform magnetic field is directly proportional to its velocity as

• $v^2$

• $\frac{1}{v}$

• $\sqrt{v}$

• $v^0$