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
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(a) 5 H |
(b) 10 H |
(c) 11 H |
(d) 12 H |
(c) 11 H
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Photo cells are used for the
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(a) Reproduction of pictures from the cinema film |
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(b) Reproduction of sound from the cinema film |
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(c) Automatic switching of street light |
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(d) (b) and (c) both |
Two parallel slits 0.6 mm apart are illuminated by light source of wavelength 6000 Å. The distance between two consecutive dark fringes on a screen 1 m away from the slits is
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(a) 1 mm |
(b) 0.01 mm |
(c) 0.1 m |
(d) 10 m |
The figure shows a double slit experiment P and Q are the slits. The path lengths PX and QX are nλ and (n+2)λ respectively, where n is a whole number and λ is the wavelength. Taking the central fringe as zero, what is formed at X
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(a) First brigh |
(b) First dark |
(c) Second bright |
(d) Second dark |
In the Millikan's experiment, the distance between two horizontal plates is 2.5 cm and the potential difference applied is 250 V. The electric field between the plates will be
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(a) 900 V/m |
(b) 10000 V/m |
(c) 625 V/m |
(d) 6250 V/m |
A calcite crystal is placed over a dot on a piece of paper and rotated, on seeing through the calcite one will be see
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(a) One dot |
(b) Two stationary dots |
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(c) Two rotating dots |
(d) One dot rotating about the other |