Question

Two capacitor c1=2uf and c2=4uf are connected in series and a potential difference (p.d) of 1200v is applied across it the potential difference across 2uf will be

Answer 1

The potential difference across 2uf will be 800V

Answer 2

two capacitors C1 = 2uF and C2 = 4uF are connected in series so, equivalent capacitance is Ceq = C1.C2/(C1 + C2) = 2 × 4/(2 + 4) = 4/3 uF

we know,
Q = CV
where Q is charge , C is the capacitance of capacitor and V is the potential difference.

now, Qnet in circuit = equivalent capacitance of capacitors attached in circuit × potential difference
Qnet = 1200 × 4/3 = 1600uC

both the capacitors are in series so, charge passing through both are same. e.g., Q = 1600uC
hence, Q = CV
here, C = 2uF , Q = 1600 uC
now, V = 1600uC/2uF = 800v

hence, potential difference across 2uF is 800v