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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The number of photo-electrons emitted per second from a metal surface increases when
|
(a) The energy of incident photons increases |
|
(b) The frequency of incident light increases |
|
(c) The wavelength of the incident light increases |
|
(d) The intensity of the incident light increases |
The reciprocal of resistance is
|
(a) Conductance |
(b) Resistivity |
(c) Voltage |
(d) None of the above |
Two resistances 
and 
when connected in series and parallel with 120 V line, power consumed will be 25 W and 100 W respectively. Then the ratio of power consumed by to that consumed by will be
|
(a) 1 : 1 |
(b) 1 : 2 |
(c) 2 : 1 |
(d) 1 : 4 |
A wire when connected to 220V mains supply has power dissipation 
. Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is 
. Then 
is
|
(a) 1 |
(b) 4 |
(c) 2 |
(d) 3 |
Which statement is correct
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(a) N-type germanium is negatively charged and P-type germanium is positively charged |
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(b) Both N-type and P-type germanium are neutral |
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(c) N-type germanium is positively charged and P-type germanium is negatively charged |
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(d) Both N-type and P-type germanium are negatively charged |