A parallel plate capacitor carries a charge q. The distance between the plates is doubled by application of a force. The work done by the force is
|
(a) Zero |
(b) |
(c) |
(d) |
(c) 
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The ratio of secondary to primary turns is 9 : 4. If power input is P, what will be the ratio of power output (neglect all losses) to power input
|
(a) 4 : 9 |
(b) 9 : 4 |
(c) 5 : 4 |
(d) 1 : 1 |
A magnet makes 40 oscillations per minute at a place having magnetic field intensity of 0.1 × 10–5 T. At another place, it takes 2.5 sec to complete one vibration. The value of earth’s horizontal field at that place is
|
(a) 0.25 × 10–6 T |
(b) 0.36 × 10–6 T |
(c) 0.66 × 10–8 T |
(d) 1.2 × 10–6 T |
There are two equipotential surface as shown in figure. The distance between them is r. The charge of –q coulomb is taken from the surface A to B, the resultant work done will be
|
(a) |
(b) |
(c) |
(d) |
Plate voltage of a triode is increased from 200 V to 225 V. To maintain the plate current, change in grid voltage from 5V to 5.75 V is needed. The amplification factor is
|
(a) 40 |
(b) 45 |
(c) 33.3 |
(d) 25 |
