Capacitance in Parallel and Series: Understanding Charge and Voltage Changes

(a) The potential difference across C1 is the same as previously. When C2 is added in parallel, the voltage across each capacitor is the same and equal to the voltage of the battery.

(b) The charge q1 on C1 is now less than previously. When C2 is added in parallel, the total charge is distributed between C1 and C2. Therefore, the charge on C1 decreases.

(c) The equivalent capacitance C12 of C1 and C2 in parallel is greater than C1. The total capacitance when capacitors are connected in parallel is the sum of the individual capacitances.

(d) The charge stored on C1 and C2 together is equal to the charge stored previously on C1. The addition of C2 in parallel does not change the total charge stored.

If C2 is added in series, the answers would be:

(a) The potential difference across C1 is the same as previously. When capacitors are in series, the total voltage across the combination is divided between the capacitors.

(b) The charge q1 on C1 is the same as previously. When capacitors are in series, the charge on each capacitor is the same.

(c) The equivalent capacitance C12 of C1 and C2 in series is less than C1. The reciprocal of the equivalent capacitance is equal to the sum of the reciprocals of the individual capacitances.

(d) The charge stored on C1 and C2 together is the same as previously on C1. When capacitors are in series, the total charge stored is the same as the charge on each capacitor.