12 cells each having same emf are connected in series with some cells wrongly connected. The arrangement is connected in series with an ammeter and two cells which are in series. Current is 3 A when cells and battery aid each other and is 2 A when cells and battery oppose each other. The number of cells wrongly connected is
|
(a) 4 |
(b) 1 |
(c) 3 |
(d) 2 |
(b) 1
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Two capacitors each of capacity 2 μF are connected in parallel. This system is connected in series with a third capacitor of 12 μF capacity. The equivalent capacity of the system will be
|
(a) 16 μF |
(b) 13 μF |
(c) 4 μF |
(d) 3 μF |
Hubble's law is related with
|
(a) Comet |
(b) Speed of galaxy |
(c) Black hole |
(d) Planetary motion |
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 |
The cut-in voltage for silicon diode is approximately
| (a) 0.2 V | (b) 0.6 V | (c) 1.1 V | (d) 1.4 V |
A diffraction is obtained by using a beam of red light. What will happen if the red light is replaced by the blue light
|
(a) Bands will narrower and crowd full together |
|
(b) Bands become broader and further apart |
|
(c) No change will take place |
|
(d) Bands disappear |
The wavelength of X-rays decreases, when
|
(a) Temperature of target is increased |
|
(b) Intensity of electron beam is increased |
|
(c) K.E. of electrons striking the target is increased |
|
(d) K.E. of electrons striking the target is decreased |