Question

The self inductance of a choke coil is mH. when it is connected with a 10 VDC source then the loss of power is 20 watt. When it connected with 10 volt AC source loss of power is 10 watt. The frequency of AC source will bw-

• A. 50 Hz
• B. 60 Hz
• C. 80 Hz
• D. 100 Hz

Answer 1

The correct option is A 50 Hz

$\begin{array}{c}Whendcispassthroughtheinductornoinduv\tan ceeffectwillbetheironly\\ resis\tan cewillbetheirresis\tan ceoftheinductorbeR\\ 20=\frac{100}{R}\\ R=5\Omega \\ Xl=\omega \times 0.001\\ power=\frac{v^2}{z}\cos \varphi \\ Z=\sqrt{25+{\omega }^2\times {10}^{-6}}\\ \cos \varphi =\frac{R}{Z}=\frac{5}{Z}\\ 10=\frac{100}{Z}\frac{5}{Z}=\frac{500}{Z^2}=\frac{500}{25}+{\omega }^2\times {10}^{-6}\\ 25+{\omega }^2\times {10}^{-6}=50\\ {\omega }^2=25\times {10}^6\\ \omega =5000\end{array}$

$=50Hz$

Hence, Option $A$ is correct answer.