Explanation:
When a p‒n junction is formed then because of the difference in the concentration of charge carriers in the two regions, electrons from the n region move to the p region and holes from the p region move to the n region. Since the direction of the current is always opposite to the motion of electron, the direction of the current is from the p side to the n side.
Similarly, when the junction is forward biassed, the positive terminal of the battery is connected to the pside of the p‒n junction and the negative terminal of the battery is connected to the n side of the p‒njunction. As a result, electrons in the n side of the p‒n junction are repelled by the negative terminal of the battery and they move to the p side, where the positive terminal of the battery attracts them. Similarly, holes from the p side of the p‒n junction are repelled by the positive terminal of the battery and they move to the n side, where the negative terminal of the battery attracts them. Thus, they give diffusion current from the p side to the n side across the p‒n junction.
In reverse biassing, there is no flow of majority carriers across the junction; hence, there is not diffusion current. Here, the flow of majority carriers is opposed by the applied voltage.
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A solenoid is 1.5 m long and its inner diameter is 4.0 cm. It has three layers of windings of 1000 turns each and carries a current of 2.0 amperes. The magnetic flux for a cross-section of the solenoid is nearly
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(a) 2.5 × 10–7 weber |
(b) 6.31 × 10–6 weber |
(c) 5.2 × 10–5 weber |
(d) 4.1 × 10–5 weber |
A current of 1 ampere is passed through a straight wire of length 2.0 metres. The magnetic field at a point in air at a distance of 3 metres from either end of wire and lying on the axis of wire will be
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(a) |
(b) |
(c) |
(d) Zero |
Two slits are separated by a distance of 0.5 mm and illuminated with light of λ = 6000 Å. If the screen is placed 2.5 m from the slits. The distance of the third bright image from the centre will be
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(a) 1.5 mm |
(b) 3 mm |
(c) 6 mm |
(d) 9 mm |
Threshold wavelength for photoelectric effect on sodium is 5000 Å. Its work function is
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(a) 15 J |
(b) 16 |
(c) 4 |
(d) 4 |
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