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600
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1. An electron with a speed of 1.8 x 106 m/s is moving in a circular orbit in a uniform magnetic field of 10-4 Wb/m², the radius of the circular path of the electron is
A. 10.63 m
B. 1.063 m
C. 106.3 m
D. 0.1063 m
2. A particle of charge 1.6 x 10-19 C and mass 1.8 x 10-27 kg is moving around the path of radius 2 x 104 m with velocity 2.4 x 106 m/s. The magnetic field necessary is (in Wb/m²)
A. 13.5 x 10-6
B. 135 x 10-6
C. 0.135 x 10
D. 1.35 x 10-6
4. A Charge is fired through a magnetic field. The magnetic force acting on it is maximum when the angle between the direction of motion and magnetic field is
A. π
B. zero
C. π/2
D. π/4
6. Two straight horizontal parallel wires are carrying the same current in same direction, d is the distnace between the wires. You are povided with a small freely suspended magnetic needle. At which of the following positions will the orientation of the needle be independent of the magnitude of current in the wires?
A. At a distance d/2 from any of the wires.
B. At a distance d/2 from any of the wires in the horizontal plane.
C. Anywhere on the circumference of a vertical circle of radius d ans centre half way between the wires.
D. At points half way between the wires in the horizontal plane.
8. When a charged particle moves in a magnetic field, its kinetic energy always
A. remain constant
B. first increases then decreases.
C. decreases
D. increases
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