A potentiometer wire of length 100 cm has a resistance of 10 ohm. It is connected in series with a resistance and an accumulator of emf 2V and of negligible internal resistance. A source of emf of 10 mV is balanced against a length of 40 cm of the potentiometer wire. What is the value of external resistance?
Text Solution
Verified by ExpertsD
The current in the potentiometer wire 
is 
The potential difference across the potentiometer wire is 
current × resistance
The length of the wire is 
.
So, the potential gradient along the wire is
… .(i)
The source of emf 10 mV is balanced against a length of 40 cm of the potentiometer wire
i.e. 
or 
Using 
or 
.
Prepare Smarter with CGP Edu
Get practice questions, solutions, and test series in one place.
Write a Review
Share your experience with this question and solution.
Commentary
Send your comment, doubt, correction, or feedback to admin.
Similar Questions
Explore conceptually related problems