A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance R, connected across the given cell, has values of
(i) infinity (ii) 9.5 $Ω$ the balancing lengths on the potentiometer wire are found to be 3 m and 2.85 m, respectively. The value of internal resistance of the cell is

Question

Infinity Learn · Accepted Answer

The internal resistance of the cell is $$r=l1l2-1RHere$$, $$l1=3$$ m,$$l2=2.85$$ m,$$R=9.5$$Ω∴  $$r=32.85-1(9.5$$Ω$$)=0.152.85$$×$$9.5$$Ω$$=0.5$$Ω

Remember concepts with our Masterclasses.

Ready to Test Your Skills?

free study material