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Question: Answered & Verified by Expert
If the modulation index of an amplitude modulated wave is changed from 0 to 1 , then the transmitted power will be
PhysicsCommunication SystemAIIMSAIIMS 2018 (27 May)
Options:
  • A unchanged
  • B doubled
  • C increased by $50 \%$
  • D zero
Solution:
1975 Upvotes Verified Answer
The correct answer is: increased by $50 \%$
The transmitted power in AM wave is
$P_t=\left(1+\frac{\mu^2}{2}\right) P_c$
where $\mu$ is the modulation index and $P_c$ is the power in carrier wave.
When $\mu=0, P_t=P_c$
and when $\mu=1, P_t=\left(1+\frac{1}{2}\right) P_c=\frac{3}{2} P_c$
$\therefore$ The percentage increase in transmitted power
$=\frac{\frac{3}{2} P_c-P_c}{P_c} \times 100 \%=\frac{1}{2} \times 100 \%=50 \%$

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