In an LR-circuit, time constant is that time in which current grows from zero to the value (where 
is the steady state current)
|
(a) |
(b) |
(c) |
(d) |
(a) 
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A sky wave with a frequency 55 MHz is incident on D-region of earth's atmosphere at 45o. The angle of refraction is (electron density for D-region is 400 electron/cm3)
|
(a) 60° |
(b) 45° |
(c) 30° |
(d) 15° |
Which of the following is true for number of spectral lines in going form Layman series to Pfund series
|
(a) Increases |
(b) Decreases |
|
(c) Unchanged |
(d) May decreases or increases |
Two non-ideal identical batteries are connected in parallel. Consider the following statements
(i) The equivalent e.m.f. is smaller than either of the two e.m.f.s
(ii) The equivalent internal resistance is smaller than either of the two internal resistances
|
(a) Both (i) and (ii) are correct |
(b) (i) is correct but (ii) is wrong |
|
(c) (ii) is correct but (i) is wrong |
(d) Both (i) and (ii) are wrong |
The two bulbs as in the above question are connected in series to a 200 volt line. Then
|
(a) The potential drop across the two bulbs is the same |
|
(b) The potential drop across the 40 watt bulb is greater than the potential drop across the 100 watt bulb |
|
(c) The potential drop across the 100 W bulb is greater than the potential drop across the 40 W bulb |
|
(d) The potential drop across both the bulb is 200 volt |
An object has image thrice of its original size when kept at 8 cm and 16 cm from a convex lens. Focal length of the lens is
|
(a) 8 cm |
(b) 16 cm |
|
(c) Between 8 cm and 16 cm |
(d) Less than 8 cm |
The average e.m.f. induced in a coil in which the current changes from 2 ampere to 4 ampere in 0.05 second is 8 volt. What is the self inductance of the coil ?
|
(a) 0.1 H |
(b) 0.2 H |
(c) 0.4 H |
(d) 0.8 H |
