Principle of Wheatstone Bridge
P / Q = R / S
The value of unknown resistance S can found. as we know the value of P, Q and R. It may be remembered that the bridge is most sensitive, when all the four resistances are of the same order.
Meter Bridge
This is the simplest form of Wheatstone bridge and is specially useful for comparing resistance more accurately.
R / S = l1 /( 100 – l1)
where l1 is the length of wire from one end where null point is obtained.
Potentiometer
Potentiometer is an ideal device to measure the potential difference between two points. It consists of a long resistance wire AB of uniform cross section in which a steady direct current is set up by means of a battery.
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