Question

University of Fiji. PHYF112: Foundation Physics II Semester II, 2019 7. The diagram given below shows a combination of capacitors connected to a 12 V power supply. 3 uF 3 uFI 12 V 6 uf 16 F (i) (ii) (iii) Determine the equivalent capacitance for the combination. What is the total charge flowing in the circuit? Determine the voltage across the 3 uF capacitor.

Answer 1

i) The capacitors 3 uF and 3uF are in parallel. The net capacitance is C1 = 3+3 = 6 uF

The capacitors 6 uF and 6 uF are in parallel. The net capacitance is C2 = 6+6= 12 uF

Therefore 6 uF and 12 uF are in series. The equivalent capacitance of the circuit is

C =(1/C1+1/C2)^-1 =(1/6+1/12)^-1 = 4 uF = 4 x 10^-6 F

ii) The total charge flowing in the circuit is

Q = C . V = 4 x 12 = 48 uCoulombs = 48 x 10^-6 Coulombs

iii) The charge flowing through one of the 3 uF capacitor is half of Q = 48/2 = 24 uC

The potential difference across the 3 uF capacitor is

v = Q/3 = 24/3 = 8 Volts