Moving Charges and Magnetism · Question 6

An electron (mass 9 10-31 kg and charge 1.6 10-19 C) moving with speed c/100 (c = speed of light) is injected into a magnetic field B of magnitude 9 10-4 T perpendicular to its direction of motion. We wish to apply a uniform electric field E together with the magnetic field so that the electron does not deflect from its path. Then (speed of light c = 3 108 m s-1)

1. E is parallel to B and its magnitude is 27 102 V m-1
2. E is parallel to B and its magnitude is 27 104 V m-1
3. E is perpendicular to B and its magnitude is 27 104 V m-1
4. E is perpendicular to B and its magnitude is 27 102 V m-1

A 2 amp current is flowing through two different small circular copper coils having radii ratio 1 : 2. The ratio of their respective magnetic moments will be

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

A tightly wound 100 turns coil of radius 10 cm carries a current of 7 A. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as 4 10-7 SI units):

1. 44 mT
2. 4.4 T
3. 4.4 mT
4. 44 T

A wire carrying a current I along the positive x-axis has length L. It is kept in a magnetic field B = (2 i + 3 j - 4 k) T. The magnitude of the magnetic force acting on the wire is :

1. 5 IL
2. 5 IL
3. 3 IL
4. 3 IL

A very long conducting wire is bent in a semi-circular shape from A to B as shown in figure. The magnetic field at point P for steady current configuration is given by : [figure]

1. 0 i4R pointed away from the page
2. 0 i4R [1 - 2 ] pointed away from page
3. 0 i4R [1 - 2 ] pointed into the page
4. 0 i4R pointed into the page

A long solenoid of radius 1 mm has 100 turns per mm. If 1 A current flows in the solenoid, the magnetic field strength at the centre of the solenoid is

1. 6.28 10-2 T
2. 12.56 10-2 T
3. 12.56 10-4 T
4. 6.28 10-4 T

Given below are two statements: In light of above statements choose the most appropriate answer from the options given below.

1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct and Statement II is incorrect
4. Statement I is incorrect and Statement II is correct

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