MCQ
The energy band gap is maximum in:
- AMetals
- BSuper conductors
- CInsulators
- DSemiconductors
Explanation:
In insulators, the electrons are tightly bound with the nucleus hence, at room temperature thermal energy is not enough to push the electrons into conduction band and hence, no electrons are available for conduction.
The energy required for electron to escape out from orbit and to over come the energy gap is thus of the order of 6 eV, while for semiconductors and conductors it is (of the order of) 1 eV and 0 respectively.
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Refractive index of air is 1.0003. The correct thickness of air column which will have one more wavelength of yellow light (6000 Å) than in the same thickness in vacuum is
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(a) 2 mm |
(b) 2 cm |
(c) 2 m |
(d) 2 km |
How much kinetic energy will be gained by an α - particle in going from a point at 70 V to another point at 50 V
|
(a) 40 eV |
(b) 40 keV |
(c) 40 MeV |
(d) 0 eV |
A rod of length 20 cm is rotating with angular speed of 100 rps in a magnetic field of strength 0.5 T about it’s one end. What is the potential difference between two ends of the rod
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(a) 2.28 V |
(b) 4.28 V |
(c) 6.28 V |
(d) 2.5 V |
The state of the energy gained by valance electrons when the temperature is raised or when electric field is applied is called as
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(a) Valance band |
(b) Conduction band |
(c) Forbidden band |
(d) None of these |
Which of the following statements is not true
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(a) The resistance of intrinsic semiconductors decrease with increase of temperature |
|
(b) Doping pure Si with trivalent impurities give P-type semiconductors |
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(c) The majority carriers in N-type semiconductors are holes |
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(d) A PN-junction can act as a semiconductor diode |