Explanation:
In the forward biassing of a p−n junction, the positive terminal of the battery is connected to the p side of the p−n junction and the negative terminal of the battery is connected to the n side of the p−n junction. As a result, electrons in the n side of the p−n junction are repelled by the negative terminal of the battery and move to the p side, where the positive terminal of the battery attracts the electrons. Similarly, holes from the p side of the p−n junction are repelled by the positive terminal of the battery and move to the nside, where the negative terminal of the battery attracts the holes. Thus, they give diffusion current across the p−n junction.
In case of reverse biassing, no conduction takes place across the junction because of the diffusion of majority carriers. Hence, there is no diffusion current.
If the junction is unbiased, then diffusion current is initially maximum. But at equilibrium, diffusion current becomes equal to drift current.
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
A small rod of bismuth is suspended freely between the poles of a strong electromagnet. It is found to arrange itself at right angles to the magnetic field. This observation establishes that bismuth is
|
(a) Diamagnetic |
(b) Paramagnetic |
(c) Ferri-magnetic |
(d) Antiferro-magnetic |
A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in horizontal direction so that the pendulum now swings through the field, the pendulum will
|
(a) Keep oscillating with the old time period |
|
(b) Keep oscillating with a smaller time period |
|
(c) Keep oscillating with a larger time period |
|
(d) Come to rest very soon |
When two magnetic moments are compared using equal distance method the deflections produced are 45o and 30o. If the length of magnets are in the ratio 1 : 2, the ratio of their pole strengths is
|
(a) 3 : 1 |
(b) 3 : 2 |
(c) |
(d) 2 |
Assertion : Two electric bulbs of 50 and 100 W are given. When connected in series 50 W bulb glows more but when connected parallel 100 W bulb glows more.
Reason : In series combination, power is directly proportional to the resistance of circuit. But in parallel combination, power is inversely proportional to the resistance of the circuit.
|
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
|
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
|
(c) If assertion is true but reason is false. |
|
(d) If the assertion and reason both are false. |
Two short magnets with their axes horizontal and perpendicular to the magnetic meridian are placed with their centres 40 cm east and 50 cm west of magnetic needle. If the needle remains undeflected, the ratio of their magnetic moments 
is
|
(a) 4 : 5 |
(b) 16 : 25 |
(c) 64 : 125 |
(d) 2 : |
What percentage of original radioactive atoms is left after five half lives
|
(a) 0.3% |
(b) 1% |
(c) 31% |
(d) 3.125% |
