Q. The antenna current of an AM transmitter is $8\ A$ when only carrier is sent but increases to $8.96\ A$ when the carrier is sinusoidally modulated. The percentage modulation is
A) 50%
B) 60%
C) 65%
D) 71%
Explanation
(d) We know that $\left( \frac{I_{t}}{I_{c}} \right)^{2} = 1 + \frac{m^{2}}{2}$
Here, $I_{t} = 8.96A$ and $I_{c} = 8A$
$\therefore\left( \frac{8.96}{8} \right)^{2} = 1 + \frac{m^{2}}{2}\ or\ 1.254 = 1 + \frac{m^{2}}{2}$
or $\frac{m^{2}}{2} = 0.254$ or $m^{2} = 0.508$
or $m = 0.71 = 71\%$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.