Question

Three capacitors of capacitance C₁=1.50 ?F, C₂ =6.00 ?F, and C₃=15.0 ?F are connected to a 30.0 V battery as shown in the figure.

1. Calculate the charge on C3.

2. Calculate the voltage across C1.

Answer 1

equivalent capacitance for C! and C2 = 1.5 + 6.0 = 7.5

for C1 C2 and C3 ->   1 / [ 1 /7.5 + 1/15 ] = 5

Q = CV ;

Q = 5 e -6 * 30 = 1.5 e -4   C    <----------charge on C3 ,

voltage across C1 = Q / C = 1.5 e -4 / 8e-6 = 18.75 V <----------ans voltatge across C1

Answer 2

Ceq of C1 C2 =6+1.5=7.5 microF

Ceq' of Ceq and C3=7.5*15/(7.5+15)= 5micro F

So total charge =30*5=150 microC

So charge on c3=2/3*150=100 micro coulomb

V along c1=30/3=10 volts

Answer 3

a)

equivalent capacitance for C! and C2 = 1.5 + 6.0 = 7.5*10^-6

for C1 C2 and C3 ->   1 / [ 1 /7.5 + 1/15 ] = 5*10^-6

Q = CV ;

Q = 5*10^-6 * 30 = 1.5*10^- 4 C   

b)

voltage across C1 = Q / C = 1.5*10^ -4 / 7.5*10^-6 = 20 V