Question #83928

1 Answer
Mar 25, 2017

9V" peak"9V peak

Explanation:

From the text of the question it is clear that this pertains to Amplitude Modulation.

![electronicspost.com](useruploads.socratic.org)

Modulation index mm is a dimensionless quantity and is defined as the ratio of amplitudes of the modulating signal and of carrier. mathematically it can be stated as

m=E_m/E_Cm=EmEC

modulation index mm takes values between 0 and 10and1 and no distortion is introduced in the AM wave when
E_m <= E_CEmEC.

However, for E_m > E_CEm>EC, mm becomes greater than 11.
This will distort the the AM signal and is called over modulation.

Sometimes, this modulation index is expressed as a percentage and called as percentage modulation.

"Percent modulation"=E_m/E_Cxx100Percent modulation=EmEC×100

As shown in the figure, inserting given values we get
75=E_m/12 xx10075=Em12×100
=>E_m=75/100 xx12Em=75100×12
=>E_m=9V" peak"Em=9V peak

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-

Sometimes we express Em and EcEmandEc in terms of E_max and E_min as seen on a screen of a CRO.

As shown in the figure
E_m=(E_max-E_min)/2
and E_C=E_max-E_m
Using expression for E_m we get
E_C=(E_max+E_min)/2

these give
m=(E_max-E_min)/(E_max+E_min)