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leena19
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Homework Statement
In the potentiometer circuit shown,the balanced length l is reduced to l/2,when a resistor of resistance R is connected across the terminals of the cell E.The internal resistance of the cell E is
(1) R/2 (2)R (3) 2R (4) 3R/2 (5) 3R
http://img268.imageshack.us/img268/4080/potentiometer.png
Homework Equations
[tex]\Sigma[/tex]E = [tex]\Sigma[/tex]IR
The Attempt at a Solution
[tex]\rho[/tex] = potential gadient
R1 is the resistance of the potentiometer wire
In the 1st case, E = I*(r+R1) = [tex]\rho[/tex] * l ?
Now when the resistor R is connected parallel to E,
V = I* R = [tex]\rho[/tex]*l/2 ?
I'm not quite sure how I'm supposed to find r from this,interms of R only.
Hope someone can help.
Thank you.
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