Explanation:
When a semiconductor is doped with a donor type such as arsenic or phosphorous, which has five valence electrons, the donor atom replaces the Si or Ge atom. As a result, four out of the five electrons of the donor atom form a covalent bond by sharing an electron with four atoms of silicon. However, the fifth electron is free to move. Also, due to the breaking up of covalent bonds at room temperature, equal number of electrons and holes are produced. Thus, the total number of holes in the n-type semiconductor is less compared to the number of free electrons.
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In a potentiometer experiment, the galvanometer shows no deflection when a cell is connected across 60 cm of the potentiometer wire. If the cell is shunted by a resistance of 6Ω, the balance is obtained across 50 cm of the wire. The internal resistance of the cell is
|
(a) 0.5 Ω |
(b) 0.6 Ω |
(c) 1.2 Ω |
(d) 1.5 Ω |
A hollow metal sphere of radius 5 cm is charged so that the potential on its surface is 10 V. The potential at the centre of the sphere is
|
(a) 0 V |
(b) 10 V |
|
(c) Same as at point 5 cm away from the surface |
(d) Same as at point 25 cm away from the surface |
64 drops of mercury each charged to a potential of 10V. They are combined to form one bigger drop. The potential of this drop will be (Assume all the drops to be spherical)
|
(a) 160 V |
(b) 80 V |
(c) 10 V |
(d) 640 V |
The internal resistance of a primary cell is 4 ohm. It generates a current of 0.2 amp in an external resistance of 21 ohm. The rate at which chemical energy is consumed in providing the current is
|
(a) 0.42 J/s |
(b) 0.84 J/s |
(c) 5 J/s |
(d) 1 J/s |
A constant current i is passed through a resistor. Taking the temperature coefficient of resistance into account, indicate which of the plots shown in figure best represents the rate of production of thermal energy in the resistor
|
(a) a |
(b) b |
(c) c |
(d) d |