Question

In the transformer shown in figure, the load resistor is $50\Omega$. The turns ratio $N_1:N_2$ is 10 : 2 and the source voltage is 200 V (r.m.s). If a voltmeter across the load measures 25 V (r.m.s.), then the source resistance $R_S$ is (power loss is negligible)

• A. $450\Omega$
• B. $750\Omega$
• C. $2000\Omega$
• D. $100\Omega$

Answer 1

The correct option is C $2000\Omega$

$\begin{array}{c}\frac{d{N}_1}{N_2}=\frac{V_1}{V_2}=\frac{i_2}{i_2}{P}_{out}=P_{in}\\ i_{load}=\frac{v}{R}=\frac{25}{50}=0.5A\\ \frac{N_1}{N_2}=\frac{i_2}{i_1}\\ \Rightarrow \frac{10}{2}=\frac{0.5}{i_1}\\ \Rightarrow \frac{1}{10}=0.1\\ R_S=\frac{v}{i}\\ \frac{200}{0.1}=2000\Omega \\ Hence,\\ Weget\\ R_S=2k\Omega \end{array}$