2. Electric Potential and Capacitance
medium

Two identical parallel plate capacitors are connected in series to a battery of $100\,V$. A dielectric slab of dielectric constant $4.0$ is inserted between the plates of second capacitor. The potential difference across the capacitors will now be respectively

A

$50\, V$, $50\, V$

B

$80 \,V$, $20\, V$

C

$20\, V$, $80\, V$

D

$75\, V$, $25\, V$

Solution

(b) ${C_{eq}} = \frac{{C \times 4C}}{{(C + 4C)}} = \frac{{4C}}{5}$
$Q = {C_{eq}}.V = \frac{{4C}}{5} \times 100 = 80\,C$
Hence ${V_1} = \frac{Q}{{{C_1}}} = \frac{{80C}}{{{C_1}}} = 80\,V$
and ${V_2} = \frac{{80C}}{{4C}} = 20\,V$

Standard 12
Physics

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