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.
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(a) Metals |
(b) Superconductors |
(c) Insulators |
(d) Semiconductors |
The Bohr model of atoms
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(a) Assumes that the angular momentum of electrons is quantized |
|
(b) Uses Einstein’s photo-electric equation |
|
(c) Predicts continuous emission spectra for atoms |
| (d) Predicts the same emission spectra for all types of atoms |
Consider two points 1 and 2 in a region outside a charged sphere. Two points are not very far away from the sphere. If E and V represent the electric field vector and the electric potential, which of the following is not possible
|
(a) | |
(b) | |
|
(c) | |
(d) | |
A parallel beam of monochromatic light of wavelength 5000 Å is incident normally on a single narrow slit of width 0.001 mm. The light is focused by a convex lens on a screen placed on the focal plane. The first minimum will be formed for the angle of diffraction equal to
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(a) 0o |
(b) 15o |
(c) 30o |
(d) 60o |
A boy stands straight infront of a mirror at a distance of 30 cm away from it. He sees his erect image whose height is 
of his real height. The mirror he is using is
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(a) Plane mirror |
(b) Convex mirror |
(c) Concave mirror |
(d) Plano-convex mirror |
In the following atoms and moleculates for the transition from n = 2 to n = 1, the spectral line of minimum wavelength will be produced by
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(a) Hydrogen atom |
(b) Deuterium atom |
(c) Uni-ionized helium |
(d) di-ionized lithium |
