state and explain the principles of wheat stone's
Answers
It is a bridge in which four resistance are arranged with a cell and a galvanometer.
Fig. (shown in attachment)
In the balanced situation of the bridge P/Q = R/S
The potential difference between the points A and B is zero and no current flows through the galvanometer
The balance point is obtained when galvanometer shows no deflection.
A Wheatstone bridge is an electrical circuit which is used to measure an unknown electrical resistance. The resistance is determined by balancing two legs of a bridge circuit, one of the legs is the unknown component.
It can be utilized to find the resistance of a resistor. It can also be used with sensors like thermistors for measurement. R4, the variable resistor is adjusted till the voltmeter shows 0 volts. The bridge is considered to be balanced at this point and R1 / R2 = R3 / R4.
Explanation
If Rx is the unknown resistance to be measured
R1, R2, and R3 are the resistors whose resistance is known
R2 resistance is adjustable
If known leg R2 / R1 = Rx / R3 in the unknown leg
then voltage between B and D the two midpoints = 0
no current flows through the galvanometer Vg
In case the bridge is unbalanced, the direction of the current will show whether R2 is too low or too high. R2 is varied till the voltmeter reads zero that means there is no current flowing through the galvanometer.