state the principle of working of a meter bridge.Draw the circuit diagram for finding an unknown resistance using meter bridge
Answers
Answer:
i) Meter bridge works on the principle of Wheatstone bridge
Wheatstone bridge
The connections are made as in the circuit. During balance condition, no current flows through the galvanometer
\therefore \frac{P}{Q}=\frac{R}{S}
Meter bridge
The length of the wire AB is 1m = 100 cm.
S is the unknown resistance
R is the resistance chosen from the resistance both Galvanometer G is connected to a Jockey. The Jockey is moved on the wire AB to obtain the null point. Let the null point be obtained at P, then
the resistance of AP\alpha L and resistance of PB\alpha (100-l)
from the Wheatstone bridge principle
\frac{R}{S}=\frac{l}{100-l}
known resistance
S=\frac{R(100-l)}{l}
(ii) Case 1
\frac{R}{S}=\frac{40}{60}=\frac{2}{3}---(1)
Case 2
\frac{R(30+S)}{30S}=1 ----(2)
From (1) and (2)
\Rightarrow \frac{30}{30+S}=\frac{2}{3}
\Rightarrow 60+25=90
\Rightarrow S=15\Omega
From (1)
\frac{R}{15}=\frac{2}{3}
R=10\Omega
Hope this helps, sorry for answering late, have a wonderful day/night, and stay safe!
