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

Choose the correct answer: