Question

A system of two conductors is placed in air and they have net charge of +80 μC and −80 μC which causes a potential difference of 16 V between them.

1. Find the capacitance of the system.
2. If the air between the capacitor is replaced by a dielectric medium of dielectric constant 3, what will be the potential difference between the two conductors?
3. If the charges on two conductors are changed to +160 μC and −160 μC, will the capacitance of the system change? Give reason for your answer.

Answer 1

1. C = Q/V

C = `(80 xx 10^-6)/16`

= 5 × 10⁻⁶ F

= 5 μF

2. C' = KC

= 3 × 5 μF

= 15 μF

V' = `(80 xx 10^-6)/(15 xx 10^-6)`

= 5.33 V

3.  Capacitance is independent of charge and only dependent on physical characteristics (geometry, medium, plate separation). The capacitance stays at 5 μF because neither the medium nor the plate configuration changes. As a result, the capacitance remains constant.