Question

A 15-µF capacitor is charged to 40 V and then connected across an initially uncharged 25-µF capacitor. What is the final potential difference across the 25-µF capacitor?

Answer 1

40V

Step-by-step explanation:

The potential difference across the initially uncharged capacitor is still 40V since there both connected in parallel. For parallel capacitor connections, the potential difference across the terminals (ends) of the capacitors is the same for all the capacitors but the charge on each capacitor depends on it capacitance.

So in this case the uncharged capacitor is in a parallel connection with the charged 40V capacitor. The connection of 15μF capacitor across the uncharged capacitor sets up a potential difference of 40V across its ends.

Answer 2

24volts

Step-by-step explanation:

If a 15-µF capacitor is charged to 40V, the charge across the capacitor can be calculated using the formula;

Q = CV where;

Q is the charge flowing across the capacitor

C is the capacitance of the capacitor. = 15-µF

V is the voltage = 40V

Q = 15×10^-6×40

Q = 0.0006coulombs

If the charge of 0.0006coulombs is then connected across an initially uncharged 25-µF capacitor, the potential difference across the 25-µF can be calculated using the initial expression;

Q = CV

V = Q/C

V = 0.0006/25×10^-6

V = 24Volts

Therefore, the final potential difference across the 25-µF capacitor will be 24volts