Explanation:
Because of the difference in the concentration of charge carriers in the p−n junction, holes from the p side move to the n side and electrons from the n side move to the p side. This motion of charge carriers gives rise to diffusion current.
Because of this, a negative space charge region is formed in the p region and a positive space region is formed in the n region. This sets up an electric field across the junction. Thus, there is a constant electric field near the junction.
This electric field further opposes the diffusion of majority charge carriers across the junction. As a result, an electron from the p region starts moving to the n region and a hole from the n region starts moving to the p region. This sets up drift current. Thus, there is a systematic flow of charge carriers across the junction. Also, there is no net charge transfer between the two sides.
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The focal length of the objective lens of a compound microscope is
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(a) Equal to the focal length of its eye piece |
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(b) Less than the focal length of eye piece |
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(c) Greater than the focal length of eye piece |
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(d) Any of the above three |
The distance of the eye-lens from the retina is x. For a normal eye, the maximum focal length of the eye-lens:
The work function of aluminium is 4.2 eV. If two photons, each of energy 3.5 eV strike an electron of aluminium, then emission of electrons will be
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(a) Possible |
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(b) Not possible |
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(c) Data is incomplete |
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(d) Depend upon the density of the surface |
A Daniel cell is balanced on 125 cm length of a potentiometer wire. Now the cell is short-circuited by a resistance 2 ohm and the balance is obtained at 100 cm. The internal resistance of the Daniel cell is
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(a) 0.5 ohm |
(b) 1.5 ohm |
(c) 1.25 ohm |
(d) 4/5 ohm |
Assertion : When radius of circular loop carrying current is doubled, its magnetic moment becomes four times.
Reason : Magnetic moment depends on area of the loop.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
Pick out the wrong statement
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(a) In a simple battery circuit, the point of lowest potential is the negative terminal of the battery |
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(b) The resistance of an incandescent lamp is greater when the lamp is switched off |
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(c) An ordinary 100 W lamp has less resistance than a 60 W lamp |
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(d) At constant voltage, the heat developed in a uniform wire varies inversely as the length of the wire used |