A varying current in a coil changes from 10 amp to zero in 0.5 sec. If average EMF is induced in the coil is 220 volts, the self inductance of coil is
|
(a) 5 H |
(b) 10 H |
(c) 11 H |
(d) 12 H |
(c) 11 H
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An N-type and P-type silicon can be obtained by doping pure silicon with
|
(a) Arsenic and Phosphorous |
(b) Indium and Aluminium |
|
(c) Phosphorous and Indium |
(d) Aluminium and Boron |
Sodium and copper have work functions 2.3eV and 4.5eV respectively. Then the ratio of their threshold wavelengths is nearest to
|
(a) 1: 2 |
(b) 4 : 1 |
(c) 2 : 1 |
(d) 1 : 4 |
A cell of internal resistance 3 ohm and emf 10 volt is connected to a uniform wire of length 500 cm and resistance 3 ohm. The potential gradient in the wire is
|
(a) 30 mV/cm |
(b) 10 mV/cm |
(c) 20 mV/cm |
(d) 4 mV/cm |
A thin glass (refractive index 1.5) lens has optical power of -5D in air. It's optical power in a liquid medium with refractive index 1.6 will be
|
(a) 25 D |
(b) – 25 D |
(c) 1 D |
(d) None of these |
The temperature of the cold junction of thermo‑couple is 0℃ and the temperature of hot junction is T℃. The e.m.f. is E = 16T – 0.04
volts. The temperature of inversion is
|
(a) 200 ℃ |
(b) 400 ℃ |
(c) 100 ℃ |
(d) 300 ℃ |
The resistivity of a wire depends on its
|
(a) Length |
(b) Area of cross-section |
(c) Shape |
(d) Material |