Moving Charges and Magnetism

A small cube of side 1 mm is placed at the centre of a circular loop of radius 10 cm carrying a current of 2 A. The magnetic energy stored inside the cube is 10-14 J. The value of is . ( 0=4 10-7 Tm/A, =3.14)

1. 6.28
2. 6.28 10-6
3. 628
4. 6.28 10-4

A current of 30 A each flows in opposite directions in two conducting wires, placed parallel to each other at a distance of 8 cm. The magnetic field at the mid point between the two wires is μT. ( 04 =10-7 N/A2)

1. 30
2. 300
3. 150
4. 0.0

A moving coil of galvanometer when shunted with 2 resistance gives a full scale deflection for a current of 500 mA. When a resistance of 470 is connected in series it gives a full scale deflection for 10 V potential applied on it. The value of resistance of galvanometer coil is .

The charged particle moving in a uniform magnetic field of (3 i+2 j ) T has an acceleration (4 i- x2 j ) m/s2. The value of x is .

A particle of charge q and mass m is projected from origin with an initial velocity v= ( v0 2 x+ v0 2 y ). There exists a uniform magnetic field B=B0 z and a space varying electric field E=E0e- x x within the region 0 x L. After travelling a distance such that x-coordinate has changed from x=0 to x=L, the change in the kinetic energy is .

1. qE0 [1-e- L ]
2. ( v0qB02 ) [2-e-2 L ]
3. qE0 [1+e- L ]
4. q ( E0+v0B0 ) [1-e- L/2 ]

A voltmeter with internal resistance of x Ω can be used to measure up to 20 V. In order to increase its measuring range to 30 V, the required modification is to .

1. connect resistor of x2 Ω, in series with voltmeter.
2. connect resistor of x2 Ω, in parallel to voltmeter.
3. connect a resistor of x Ω in series with voltmeter.
4. connect resistor of 2x Ω in parallel to voltmeter.

An insulated wire is wound so that it forms a flat coil with N=200 turns. The radius of the innermost turn is r1=3 cm, and of the outermost turn r2=6 cm. If 20 mA current flows in it then the magnetic moment will be 10-2 A m2. The value of is .

1. 4.4
2. 2.64
3. 3.25
4. 1.2

A circular coil of radius 2 cm and 125 turns carries a current of 1 A. The coil is placed in a uniform magnetic field of magnitude 0.4 T. The axis of the coil makes an angle of 30° with the direction of the magnetic field. The torque acting on the coil is 10-4 N m. The value of is . ( =3.14)

Two identical long current carrying wires are bent into the shapes shown in the following figures. If the magnitude of magnetic fields at the centres P and Q of a semicircular arc are B1 and B2 respectively, then the ratio B1B2 is . [figure]

1. 2+ 1+
2. 1+ 1-
3. 2+ 1-
4. 1+ 2-

1 μC charge moving with velocity v= ( i-2 j+3 k ) m/s in the region of magnetic field B= (2 i+3 j-5 k ) T. The magnitude of force acting on it is 10-6 N. The value of is .