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Question
Write the principle of working of a metre bridge
Solution
Metre bridge follows the principle of Wheatstone bridge. Wheatstone bridge principle states that if four resistance P, Q, R and S are arranged to form a bridge as shown below with a cell ε and one way K between the points A and C and a galvanometer G between the points B and D, then on closing K, if galvanometer shows no deflection, the bridge is balanced.
Then, `P/Q=R/S`
P = resistance of the length l cm of the wire AD = lr
and Q = resistance of the length (100 - l) cm of the wire DC = (100 - l) × r.
where, r is the resistance per unit length of the wire.
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Which material is used for the meter bridge wire and why?
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