Moving Charges and Magnetism · Question 13

From Ampere's circuital law for a long straight wire of circular cross-section carrying a steady current, the variation of magnetic field in the inside and outside region of the wire is

1. Uniform and remains constant for both the regions.
2. A linearly increasing function of distance upto the boundary of the wire and then linearly decreasing for the outside region.
3. A linearly increasing function of distance r upto the boundary of the wire and then decreasing one with 1r dependence for the outside region.
4. A linearly decreasing function of distance upto the boundary of the wire and then a linearly increasing one of the outside region.

A closely packed coil having 1000 turns has an average radius of 62.8 cm. If current carried by the wire of the coil is 1 A, the value of magnetic field produced at the centre of the coil will be (permeability of free space = 4 10-7 H/m) nearly

1. 10-3 T
2. 10-1 T
3. 10-2 T
4. 102 T

The shape of the magnetic field lines due to an infinite long, straight current carrying conductor is

1. a plane
2. a straight line
3. circular
4. elliptical

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