Question 684: Electrostatics & Capacitance

Question

A parallel plate capacitor of capacitance $5 \mu \mathrm{F}$ is charged to $120 \mathrm{~V}$ and then connected to another uncharged capacitor. If the potential falls to $40 \mathrm{~V}$, and capacitance of the second capacitor is

Accepted Answer

Change, $Q=C V$
$\begin{aligned}
	ext{Given,} \quad & C=5 \mu \mathrm{F}=5 	imes 10^{-6} \mathrm{~F}, \mathrm{~V}=120 \mathrm{~V} \
& Q=5 	imes 10^{-6} 	imes 120
\end{aligned}$
Also, $5 	imes 10^{-6} 	imes 120=40 	imes C$
$\begin{array}{ll}
\Rightarrow & C=\frac{5 	imes 10^{-6} 	imes 120}{40}=15 	imes 10^{-6} \mathrm{~F} \
\Rightarrow & C=15 \mu \mathrm{F}
\end{array}$

Answer

5 $\mu$F

Answer

10 $\mu$F

Answer

15 $\mu$F

Answer

20 $\mu$F

Electrostatics & Capacitance

A parallel plate capacitor of capacitance 5 \mu \mathrm{F} is charged to 120 \mathrm{~V} and then connected to another uncharged capacitor. If the potential falls to 40 \mathrm{~V}, and capacitance of the second capacitor is

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