Question

A 5.0-?F capacitor and a 7.0-?F capacitor are connected in series across an 8.0-V potential source. What is the potential difference across the 5.0-?F capacitor?

A) 4.7 V

B) 0 V

C) 2.7 V

D) 8.0 V

E) 3.6V

Answer 1

remember these about Combination of capacitors

if C1 and C2 are the individual capacitor that re connected in series,

then their resultant capaciatnce 1/Cnet = 1/C1+1/C2 or Cnet   = C1C2/(C1+C2)

if c1 and C2 are connected in parallel, then their effective capacitancen is Cnet = C1+C2

also in sereis combination same amount of charge passes through each of the capacitiors

and in parallel combination, same PD (voltage) exists across each of the capacitor

so here

Cnet =   1/Cnet = (1/5) +(1/7)

1/Cnet = 0.342

Cnet = 2.91 uF

so
Qnet = CV

Qnet =- 2.91 e-6 * 8   = 23.34 uC

so finally   V1 = Qnet/C1   = 23.34/5 = 4.667 Volts ---<<<<<<needed answer

thus option A is the answer)

V2 = 23.34/7 = 3.334 Volts   ------<<<<<<<<<<extra work