Q148 / 180 · COMEDK 2018 · Physics
The value of alternating emf $E$ in the given circuit will be
- A$220 \mathrm{~V}$
- B$140 \mathrm{~V}$
- Correct answerC$100 \mathrm{~V}$
- D$20 \mathrm{~V}$
Solution
The given circuit diagram is $L-C-R$. series circuit, where
$$
\begin{aligned}
&V_{R}=80 \mathrm{~V}, V_{C}=100 \mathrm{~V} \\
&V_{L}=40 \mathrm{~V}
\end{aligned}
$$
Since, $\quad V_{C}>V_{L}$
Value of $\operatorname{emf} E$ is given as
$$
\begin{aligned}
E &=\sqrt{V_{R}^{2}+\left(V_{C}-V_{L}\right)^{2}} \\
&=\sqrt{80^{2}+(100-40)^{2}} \\
&=\sqrt{6400+3600}=100 \mathrm{~V}
\end{aligned}
$$
Hence, the correct answer is option: 'C'.