Question

Two capacitors $C_1$ and $C_2$ are connected as shown. When switch S is closed then,

• A. magnitude of charge passing through point a is $24\mu C$.
• B. magnitude of charge passing through b is $60\mu C$.
• C. magnitude of charge passing through a is zero.
• D. positive charge flow from earth to circuit through b.

Answer 1

Answer: (B), (D)

The correct options are
B magnitude of charge passing through b is $60\mu C$.
D positive charge flow from earth to circuit through b.

By $q=C_{eq}V$

$C_{eq}=\frac{C_1{C}_2}{C_1+C_2}=\frac{6}{5}\mu F$

q=$\frac{6}{5}\times 120\mu C=144\mu C$

$q_1=C_1{V}_1\Rightarrow q_1=2\times 60\mu C$

$q_1=120\mu C$

$q_2=C_2{V}_2\Rightarrow q_2=3\times 60\mu C$

$q_2=180\mu C$

$\left|△q_a\right|=|q-q_1|=|144-20|=124\mu C$

$△q_b=q_2-q_1=180-120=60\mu C$