Question

Circuit diagram of a wheatstone brigde in which Resistance 1=Resistance 2=Resistance 3=Varrying Resistance 4 = 1000ohms and Emf =20volts. The galvanometer can detect as low as 0.1milliamperes. Determine;

1. Internal resistance of the bridge being measured across the terminal.
2. Output voltage due to unbalanced conditions.
3. Current through the galvanometer for unbalanced conditions.

Small charge in the resistance that can be detected.

.

Answer 1

1.

$V= I(R_a+R_x)\\ \frac{V}{I}=R_a+R_x\\ \frac{20}{0.1*10^{-3}}=1000+R_x\\ R_x=199000 \Omega$

2.

$v= \frac{R_1}{R_3}*V_1 = \frac{R_2}{R_4}*V_1= \frac{1000}{1000}*20=20V$

3.

$I= \frac{V}{R}\\ I= \frac{20}{1000}\\ I=0.02A$