Moving Charges and Magnetism · Question 16

Two very long, straight, parallel conductors A and B carry current of 5 A and 10 A respectively and are at a distance of 10 cm from each other. The direction of current in two conductors is same. The force acting per unit length between two conductors is : ( 0 = 4 10-7 SI unit)

1. 1 10-4 N m-1 and is repulsive
2. 2 10-4 N m-1 and is attractive
3. 2 10-4 N m-1 and is repulsive
4. 1 10-4 N m-1 and is attractive

The magnetic field on the axis of a circular loop of radius 100 cm carrying current I = 2 A, at point 1 m away from the centre of the loop is given by :

1. 6.28 10-4 T
2. 3.14 10-7 T
3. 6.28 10-7 T
4. 3.14 10-4 T

A thick current carrying cable of radius 'R' carries current 'I' uniformly distributed across its cross section. The variation of magnetic field B(r) due to the cable with the distance 'r' from the axis of the cable is represented by :

1. [figure]
2. [figure]
3. [figure]
4. [figure]

An infinitely long straight conductor carries a current of 5 A as shown. An electron is moving with a speed of 105 m/s parallel to the conductor. The perpendicular distance between the electron and the conductor is 20 cm at an instant. Calculate the magnitude of the force experienced by the electron at that instant. [figure]

1. 8 10-20 N
2. 4 10-20 N
3. 8 10-20 N
4. 4 10-20 N

In the product F = q ( v B ) = q v (B i + B j + B0 k ) For q = 1 and v = 2 i + 4 j + 6 k and F = 4 i - 20 j + 12 k What will be the complete expression for B?

1. 6 i + 6 j - 8 k
2. -8 i - 8 j - 6 k
3. -6 i - 6 j - 8 k
4. 8 i + 8 j - 6 k

A uniform conducting wire of length 12a and resistance 'R' is wound up as a current carrying coil in the shape of, (i) an equilateral triangle of side 'a' (ii) A square of side 'a' The magnetic dipole moments of the coil in each case respectively are :

1. 4Ia2 and 3Ia2
2. 3 Ia2 and 3Ia2
3. 3Ia2 and Ia2
4. 3Ia2 and 4Ia2

A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is : ( 0 = 4 10-7 T m A-1)

1. 3.14 10-4 T
2. 6.28 10-5 T
3. 3.14 10-5 T
4. 6.28 10-4 T

A cylindrical conductor of radius R is carrying a constant current. The plot of the magnitude of the magnetic field B with the distance d from the centre of the conductor, is correctly represented by the figure :

1. [figure]
2. [figure]
3. [figure]
4. [figure]

Ionized hydrogen atoms and α-particles with same momenta enter perpendicular to a constant magnetic field, B. The ratio of their radii of their paths rH : r will be :

1. 1 : 2
2. 4 : 1
3. 1 : 4
4. 2 : 1

A metallic rod of mass per unit length 0.5 kg m-1 is lying horizontally on a smooth inclined plane which makes an angle of 30 with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. The current flowing in the rod to keep it stationary is

1. 7.14 A
2. 5.98 A
3. 14.76 A
4. 11.32 A