- AMajority carriers
- BMinority carriers
- CAbsent
- DNone of the above
Explanation:
P-type semiconductors are those which have a p-type impurity. A p-type impurity is a material in which the atoms have only 3 Valence Electrons. When they are added to a pure semiconductor, each atom gets bonded with 3 of atoms of the semiconductor. Between the 4th atom of the semiconductor and the atom of the impurity, there is an empty space due to lack of an electron. This empty space is known as a hole. Because of a large existence of P-type material in a p-type semiconductor, it has more holes as compared to free electrons. Hence holes are majority carriers.
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A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one- fourth of the material remains is
|
(a) 1080 |
(b) 2430 |
(c) 3240 |
(d) 4860 |
Which one is correct relation for thermionic emission
|
(a) |
(b) |
(c) |
(d) |
A photon of energy 8 eV is incident on a metal surface of threshold frequency 1.6
, then the maximum kinetic energy of photoelectrons emitted is (h = 6.6
|
(a) 4.8 eV |
(a) 4.8 eV |
(c) 1.4 eV |
(d) 0.8 eV |
Four wires AB, BC, CD, DA of resistance 4 ohm each and a fifth wire BD of resistance 8 ohm are joined to form a rectangle ABCD of which BD is a diagonal. The effective resistance between the points A and B is
|
(a) 24 ohm |
(b) 16 ohm |
(c) |
(d) |
Two normal uniform magnetic field contain a magnetic needle making an angle 60° with F. Then the ratio of is
| (a) 1 : 2 | (b) 2 : 1 |
(c) |
(d) 1 : |
An external resistance R is connected to a battery of e.m.f. V and internal resistance r. The joule heat produced in resistor R is maximum when R is equal to
|
(a) r |
(b) |
(c) 2r |
(d) Infinitely large |
Assertion : Electric lines of force cross each other.
Reason : Electric field at a point superimpose to give one resultant electric field.
|
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
|
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
|
(c) If assertion is true but reason is false. |
|
(d) If assertion is false but reason is true. |
It is desired to photograph the image of an object placed at a distance of 3m from the plane mirror. The camera which is at a distance of 4.5 m from the mirror should be focussed for a distance of
| (a) 3m | (b) 4.5m | (c) 6m | (d) 7.5 m |
A star producing light of wavelength 6000 Å moves away from the earth with a speed of 5 km/sec. Due to Doppler effect the shift in wavelength will be ( c = 3
|
(a) 0.1 Å |
(b) 0.05 Å |
(c) 0.2 Å |
(d) 1 Å |