A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 
away, the number of electrons emitted by photo cathode would
|
(a) Decrease by a factor of 2 |
(b) Increase by a factor of 2 |
|
(c) Decrease by a factor of 4 |
(d) Increase by a factor of 4 |
(d) Increase by a factor of 4
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A current of 10A is passing through a long wire which has semicircular loop of the radius 20cm as shown in the figure. Magnetic field produced at the centre of the loop is
|
(a) 10 πμT |
(b) 5 πμT |
(c) 4 πμT |
(d) 2 πμT |
In a radioactive reaction 
, the number of α - particles emitted is
|
(a) 7 |
(b) 6 |
(c) 5 |
(d) 4 |
The diode shown in the circuit is a silicon diode. The potential difference between the points A and B will be
|
(a) 6 V |
(b) 0.6 V |
(c) 0.7 V |
(d) 0 V |
The resistance of the series combination of two resistance is S. When they are joined in parallel the total resistance is P. If S = nP, then the minimum possible value of n is
|
(a) 4 |
(b) 3 |
(c) 2 |
(d) 1 |
To get the maximum current from a parallel combination of n identical cells each of internal resistance r in an external resistance R, when
|
(a) R >> r |
(b) R << r |
(c) R = r |
(d) None of these |
Magnetic field due to 0.1 A current flowing through a circular coil of radius 0.1 m and 1000 turns at the centre of the coil is
|
(a) 2 |
(b) 4.31 |
(c) 6.28 |
(d) 9.81 |
In a primary coil 5A current is flowing on 220 volts. In the secondary coil 2200V voltage produces. Then ratio of number of turns in secondary coil and primary coil will be
|
(a) 1 : 10 |
(b) 10 : 1 |
(c) 1 : 1 |
(d) 11 : 1 |
