Explanation:
In insulators, the electrons are very tightly bound to the nucleus. At a room temperature, thermal energy is not enough to push electrons into conduction band. The energy band gap is very high. Thus the conduction band is empty and the valence band is filled with electrons.
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The number of dry cells, each of e.m.f. 1.5 volt and internal resistance 0.5 ohm that must be joined in series with a resistance of 20 ohm so as to send a current of 0.6 ampere through the circuit is
|
(a) 2 |
(b) 8 |
(c) 10 |
(d) 12 |
Nuclear fusion is common to the pair
| (a) Thermonuclear reactor, uranium based nuclear reactor |
| (b) Energy production in sun, uranium based nuclear reactor |
| (c) Energy production in sun, hydrogen bomb |
| (d) Disintegration of heavy nuclei, hydrogen bomb |
The core of a transformer is laminated to reduce energy losses due to
|
(a) Eddy currents |
(b) Hysteresis |
|
(c) Resistance in winding |
(d) None of these |
$1:1$
$1:2$
$\pi:2$
$2:\pi$
A certain amount of current when flowing in a properly set tangent galvanometer, produces a deflection of 45°. If the current be reduced by a factor of 
, the deflection would
| (a) Decrease by 30° | (b) Decrease by 15° | (c) Increase by 15° | (d) Increase by 30° |
The imaginary line passing through the pole and the center of curvature of the curved mirror is called its _______.