GATE 2026 IN – Question 52
An amplitude-modulated voltage signal $x(t)$ drives a load of $1\ \Omega$, where $x(t)=K\cos(300\pi t)+L\cos(240\pi t)+L\cos(360\pi t)$. If the efficiency is 60% and the carrier power is 50 W, the value of $L$ is ________ V.
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Correct answer: (A) 8.66
Explanation
Let $P_{sb}$ be the combined sideband power. Efficiency is $P_{sb}/(P_c+P_{sb})$, so $0.60=P_{sb}/(50+P_{sb})$, giving $P_{sb}=75\ \mathrm W$.
Each sideband has peak amplitude $L$ and power $L^2/(2R)$. Together they deliver $L^2/R$. With $R=1\ \Omega$, $L=\sqrt{75}=8.66\ \mathrm V$, **A**.