The antenna current of an AM transmitter is 8 A when only the carrier is sent, but it increases to 8.93 A when the carrier is modulated by a single sine wave. Find the percentage modulation.

Explanation

The modulated or total power carried by AM wave `P_(tau)=P_(C)(1+(m^(2))/(2))` Id R is load resistance, `I_(m)` is the current when carrier is modulated and `I_(c)` the current when un-modulated, then
`(P_(tau))/(P_(C))=(I_(m)""^(2)R)/(I_(c)""^(2)R)" ":.I+(m^(2))/(2)=(I_(m)""^(2)R)/(I_(c)""^(2)R)`
Given `I_(m)=8.93A,I_(c)=8A`
`:.m^(2)=2[((8.93)/(8.0))^(2)-1]:.m=0.7`
Therefore, percentage modulation `=70%`