JEE Main 2016PhysicsCurrent ElectricityMediumMCQ

JEE Main 2016 — Current Electricity Question with Solution

JEE Main 2016 (09 Apr Online)

Question



In the circuit shown, the resistance r is a variable resistance. If for r=fR , the heat generation in r is maximum then the value of f is

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Show full solutionCorrect option: A
Correct answer
A12

Step-by-step explanation



Power in “r”

P= I 2 2 r= [ I× R R+r ] 2 r= I 2 R 2  r ( R+r ) 2

P= [ E R+ R×fR R+fR ] 2 R 2 ( fR ) ( R+fR ) 2 = E 2 R 2 fR R 2 [ 1+ f ( f+1 ) ] 2 R 2 ( 1+f ) 2

P= E 2 f R ( 1+2f ) 2

For P( max )  dP df =0

E 2 R =[ ( 1+2f ) 2 −f{ 2( 1+2f )( 0+2 ) } ( 1+2f ) 2 ]=0

( 1+2f ) 2 =4f( 1+2f )

1+2f=4f

f= 1 2

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About this question

This is a previous-year question from JEE Main 2016, covering the Current Electricity chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.