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JEE Main 202226 JulyEvening Shift

Exam: JEE Main
Year: 2022
Date: 26 July
Shift: Evening Shift
Subject: Physics
Chapter: Communication System

JEE Main 2022 · 26 July · Evening Shift · Physics · Communication System

The maximum and minimum voltage of an amplitude modulated signal...

The maximum and minimum voltage of an amplitude modulated signal are

60V

and

20V

respectively. The percentage modulation index will be

Options

A $0 . 5 %$
B $50 %$
C $2 %$
D $30 %$

Correct answer

B. $50 %$

Step-by-step solution

If amplitude of carrier wave is ${A}_{c}$ and amplitude of message wave is ${A}_{m}$ ,
${A}_\max = {A}_{c} + {A}_{m}$ and ${A}_\min = {A}_{c} - {A}_{m}$
Modulation index,
${M}_{i} = \dfrac{{A}_{m}}{{A}_{c}} = \dfrac{\dfrac{{A}_\max - {A}_\min}{2}}{\dfrac{{A}_\max + {A}_\min}{2}} = \dfrac{60 - 20}{60 + 20} = \dfrac{1}{2} = 50 %$

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