Explanation:
Fusion reaction takes place at temperatures around 107k. It requires this high temperature so that nucleus start moving at rapidly speed, which in turn increases their kinetic, so that they overcome the repulsion between them and can come together.
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When N-type of semiconductor is heated
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(a) Number of electrons increases while that of holes decreases |
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(b) Number of holes increases while that of electrons decreases |
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(c) Number of electrons and holes remains same |
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(d) Number of electrons and holes increases equally |
A potentiometer wire of length 1 m and resistance 10 W is connected in series with a cell of emf 2V with internal resistance 1 W and a resistance box including a resistance R. If potential difference between the ends of the wire is 1 mV, the value of R is
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(a) 20000 W |
(b) 19989 W |
(c) 10000 W |
(d) 9989 W |
In a wire of circular cross-section with radius r, free electrons travel with a drift velocity V when a current I flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is 2V
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(a) 2I |
(b) I |
(c) I/2 |
(d) I/4 |
A transformer with efficiency 80% works at 4 kW and 100 V. If the secondary voltage is 200 V, then the primary and secondary currents are respectively
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(a) 40 A, 16 A |
(b) 16 A, 40 A |
(c) 20 A, 40 A |
(d) 40 A, 20 A |
The dispersive powers of glasses of lenses used in an achromatic pair are in the ratio 5 : 3. If the focal length of the concave lens is 15 cm, then the nature and focal length of the other lens would be
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(a) Convex, 9 cm |
(b) Concave, 9 cm |
(c) Convex, 25 cm |
(d) Concave, 25 cm |