GATE 2022 PH – Question 30
A supply has open-load voltage 5 V and internal resistance RS. A load RL receives 4 V. Find RL/RS, nearest integer.
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Correct answer: 4
Explanation
The source is a voltage $V_0=5$ V in series with an internal resistance $R_S$, connected to a load $R_L$. The load voltage is given by the voltage divider:
$$V_L=V_0\,\frac{R_L}{R_L+R_S}.$$
With $V_L=4$ V:
$$\frac{R_L}{R_L+R_S}=\frac45\;\Rightarrow\;5R_L=4R_L+4R_S\;\Rightarrow\;R_L=4R_S .$$
$$\frac{R_L}{R_S}=\mathbf{4}.$$