A variable capacitor and an electroscope are connected in parallel to ...
Explanation:An electroscope is a device which measures the potential difference. If it is connected in parallel to the capacitor, the potential across it will be equal to the potential across the capacitor, which is equal to the potential across the battery. On decreasing the battery potential, the potential difference across the electroscope reduces and hence the reading reduces. While the capacitor is connected to the battery, Placing a dielectric between the plates, or decreasing the distance between the plates or increasing the area of the plates will not change the potential difference across it; since it will always remain equal to the potential difference maintained by the battery. In the cases B, C and D, The capacitance of the capacitor , however increases ; but this increase happens due to increase in the charge stored in the capacitor while the potential remains constant.
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A variable capacitor and an electroscope are connected in parallel to ...
Explanation:
Variable capacitor and electroscope are connected in parallel to a battery. When a battery is connected to a parallel combination of a variable capacitor and an electroscope, the electroscope reads the voltage across the capacitor plates. The voltage across the capacitor is equal to the battery voltage. Therefore, the electroscope reading depends on the battery potential.
(a) Decreasing the battery potential: If we decrease the battery potential, the voltage across the capacitor plates will also decrease. As a result, the electroscope reading will also decrease.
(b) Placing a dielectric between the plates: If we place a dielectric between the plates, the capacitance of the capacitor will increase. As a result, the voltage across the capacitor plates will decrease. But the electroscope reading will not be affected because the charge on the plates will remain the same.
(c) Increasing the area of overlapping of the plates: If we increase the area of overlapping of the plates, the capacitance of the capacitor will increase. As a result, the voltage across the capacitor plates will decrease. But the electroscope reading will not be affected because the charge on the plates will remain the same.
(d) Decreasing the distance between the plates: If we decrease the distance between the plates, the capacitance of the capacitor will increase. As a result, the voltage across the capacitor plates will decrease. But the electroscope reading will not be affected because the charge on the plates will remain the same.
Conclusion:
Hence, the correct answer is option 'A' that is decreasing the battery potential.