direct current bridges. a wheatstone bridge can be used to measure resistance by comparing unknown...
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Direct Current Bridges
A Wheatstone bridge can be used to measure resistance by comparing unknown resistor against precision resistors of known value,
When the voltage between A and B is equal zero .
Then the voltage for R1 is equal to the voltage for R2
I1 R1 = I 2 R 2 (1) I3 R3 = I4 R4 (2)
I Galvanometer is equal zero then
I1 = I3 , I2= I4 (3)Divide (1)/(I2 2)
or
Calculate the value of Rx if the bridge is balanced
R1 Rx = R2 R3
We can calculate Vth and rth by the following:
* First Vth : Using voltage Kirchhoff law Vth =V1 − V2 = I1 R1 − I2 R2
=
seconded rth
Calculate the current flowing through Galvanometer in the figure bellow: