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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A battery is charged at a potential of 15 V for 8 hours when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 hours. The mean terminal voltage during discharge is 14 V. The "Watt-hour" efficiency of the battery is
|
(a) 82.5% |
(b) 80 % |
(c) 90% |
(d) 87.5% |
A divergent lens will produce
|
(a) Always a virtual image |
(b) Always real image |
|
(c) Sometimes real and sometimes virtual |
(d) None of the above |
Kirchhoff's second law is based on the law of conservation of
|
(a) Charge |
(b) Energy |
|
(c) Momentum |
(d) Sum of mass and energy |
A long solenoid has a radius a and number of turns per unit length is n. If it carries a current i, then the magnetic field on its axis is directly proportional to
|
(a) ani |
(b) ni |
(c) |
(d) |
