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A conducting rod AC of length 4l is rotated about a point O in a uniform magnetic field 
directed into the paper. AO = l and OC = 3l. Then
|
(a) |
(b) |
(c) |
(d) |
Two identical parallel plate capacitors are connected in series to a battery of 100 V. A dielectric slab of dielectric constant 4.0 is inserted between the plates of second capacitor. The potential difference across the capacitors will now be respectively
|
(a) 50 V, 50 V |
(b) 80 V, 20 V |
(c) 20 V, 80 V |
(d) 75 V, 25 V |
When a point source of light is at a distance of one metre from a photo cell, the cut off voltage is found to be V. If the same source is placed at 2 m distance from photo cell, the cut off voltage will be
|
(a) V |
(b) V/2 |
(c) V/4 |
(d) V/ |
In a dark room of photography, generally red light is used. The reason is
|
(a) Most of the photographic films are not sensitive to red light |
|
(b) The frequency for red light is low and hence the energy hv of photons is less |
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(c) (a) and (b) both |
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(d) None of the above |
Which of the following spectral series in hydrogen atom give spectral line of 4860 Å
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(a) Lyman |
(b) Balmer |
(c) Paschen |
(d) Brackett |
An ideal transformer has 500 and 5000 turn in primary and secondary windings respectively. If the primary voltage is connected to a 6V battery then the secondary voltage is
|
(a) 0 |
(b) 60 V |
(c) 0.6 V |
(d) 6.0 V |
The outer sphere of a spherical air capacitor is earthed. For increasing its capacitance
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(a) Vacuum is created between two spheres |
|
(b) Dielectric material is filled between the two spheres |
|
(c) The space between two spheres is increased |
|
(d) The earthing of the outer sphere is removed |
