Question

An AM modulator develops an unmodulated power of 400 W and power of 450 W when modulated with modulation index \( \mu \) across the resistive load. Then the value of \( \mu \) is

• A. 0.5
• B. 0.6
• C. 0.7
• D. 0.8

Answer 1

The Correct Option is A

The total power in AM is given by \[ P_{\text{total}} = P_c \left( 1 + \frac{\mu^2}{2} \right) \] where \( P_c = 400 \) W. Given \( P_{\text{total}} = 450 \) W, \[ 450 = 400 \times \left( 1 + \frac{\mu^2}{2} \right) \] \[ 1.125 = 1 + \frac{\mu^2}{2} \] \[ \frac{\mu^2}{2} = 0.125 \implies \mu = 0.5 \] \(\text{Conclusion:}\) The modulation index is 0.5, as given by option (a).