Question
(i) State the principle of working of a potentiometer.
(ii) In the following potentiometer circuit, AB is a uniform wire of length 1 m and resistance 10 Ω. Calculate the potential gradient along the wire and balance length AO (= l)
Solution
i)
Principale of potentiometer: The potential difference across any two points of current carrying wire, having uniform cross-sectional area and material, of the potentiometer is directly proportional to the length between the two points.
That is, V 
Proof:
V = IR = I 
i.e., V = 
For unifrom current and cross- sectional area, we have
ii)
Given,
E = 2 V; R = 15 
; RAB = 10 
Potential difference across the wire, = 
Therefore, potential gradient = 0.8/1 = 0.8 V/ m
Potential difference across AO = 
Therefore,
Length, AO = 
= 
; which is the required balance length of the wire.
