A narrow electron beam passes undeviated through an electric field E = 3 
and an overlapping magnetic field B = 2 
. If electric field and magnetic field are mutually perpendicular. The speed of the electrons is
|
(a) 60 m/s |
(b) 10.3 |
(c) 1.5 |
(d) 0.67 |
(c) 1.5 
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A power line lies along the east-west direction and carries a current of 10 ampere. The force per metre due to the earth's magnetic field of 
is
|
(a) |
(b) |
(c) |
(d) |
Faraday's laws of electrolysis are related to
|
(a) The atomic number of positive ion |
(b) The equivalent weight of electrolyte |
|
(c) The atomic number of negative ion |
(d) The velocity of positive ion |
Photoelectric emission is observed from a metallic surface for frequencies 
and 
of the incident light rays (
. If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of 1 : k, then the threshold frequency of the metallic surface is
|
(a) |
(b) |
(c) |
(d) |
Tangent galvanometer is used to measure
| (a) Steady currents | (b) Current impulses |
| (c) Magnetic moments of bar magnets | (d) Earth's magnetic field |
Chromatic aberration of lens can be corrected by
|
(a) Reducing its aperature |
|
(b) Proper polishing of its two surfaces |
|
(c) Suitably combining it with another lens |
|
(d) Providing different suitable curvature to its two surfaces |
Two bulbs of 500 watt and 200 watt are manufactured to operate on 220 volt line. The ratio of heat produced in 500 W and 200 W, in two cases, when firstly they are joined in parallel and secondly in series, will be
|
(a) |
(b) |
(c) |
(d) |
Radon (Ra) decays into Polonium (
by emitting an α - particle with half-life of 4 days. A sample contains 6.4 
atoms of Rn. After 12 days, the number of atoms of 
left in the sample will be
|
(a) 3.2 |
(b) 0.53 |
(c) 2.1 |
(d) 0.8 |
A dielectric slab of thickness d is inserted in a parallel plate capacitor whose negative plate is at x = 0 and positive plate is at x = 3d. The slab is equidistant from the plates. The capacitor is given some charge. As one goes from 0 to 3d
|
(a) The magnitude of the electric field remains the same |
|
(b) The direction of the electric field remains the same |
|
(c) The electric potential increases continuously |
|
(d) b, c |
The mobility of free electron is greater than that of free holes because
|
(a) The carry negative charge |
|
(b) They are light |
|
(c) They mutually collide less |
|
(d) They require low energy to continue their motion |
