- AThe capacitance increases.
- BThe potential difference increases.
- CThe total charge increases.
- DThe charge and potential difference remain the same.
Explanation:
Capacitance of a parallel plate capacitor.
$\text{C}=ε0\text{AdC}=ε0\text{Ad}$
A parallel plate capacitor is charged (battery is disconnected) then the plates are pulled apart, the capacitance decreases while the charge remains the same.
$\because$ Potentialdifference = ChargeCapacitance∵Potentialdifference = ChargeCapacitance.
$\therefore$ potential difference increases.
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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 |
The core of a transformer is laminated so that
|
(a) Ratio of voltage in the primary and secondary may be increased |
|
(b) Rusting of the core may be stopped |
|
(c) Energy losses due to eddy currents may be reduced |
|
(d) Change in flux is increased |
The capacity of a condenser in which a dielectric of dielectric constant 5 has been used, is C. If the dielectric is replaced by another with dielectric constant 20, the capacity will become
|
(a) |
(b) 4C |
(c) |
(d) 2C |
For television broadcasting, the frequency employed is normally
|
(a) 30-300 MHz |
(b) 30-300 GHz |
(c) 30-300 KHz |
(d) 30-300 Hz |
A rod of length 20 cm is rotating with angular speed of 100 rps in a magnetic field of strength 0.5 T about it’s one end. What is the potential difference between two ends of the rod
|
(a) 2.28 V |
(b) 4.28 V |
(c) 6.28 V |
(d) 2.5 V |
We can reduce eddy currents in the core of transformer
|
(a) By increasing the number of turns in secondary coil |
|
(b) By taking laminated core |
|
(c) By making step-down transformer |
|
(d) By using a weak ac at high potential |