Question

what is a metre Bridge.?

Answer 1

$\Large\underline\mathfrak{Question}$

What is a metre Bridge.?

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→ From the Diagram.

$\Large\bold\star\underline{\underline\textbf{Meter bridge\:}}$

→ A metre bridge is a practical form of wheatstone bridge.

→ Wheatstone bridge is an arrangement of four resistance is used for measuring one unknown resistance in terms of other three residences.

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$\Large\bold\star\underline{\underline\textbf{Circuit arrangement\:}}$

→ Check the Diagram first given with this answer.

» It consists of a wire AC of constantan or manganin of 1 metre length and uniform cross section area.

» This wire is stretched between the copper strips on a horizontal wooden board.

» A metre scale is fixed on the wooden board parallel to the length of the wire.

» A resistance box R is connected as shown in the figure. An unknown resistance S is also connected.

» A Jockey is slided on the wire. One terminal of the Jockey is connected to the galvanometer and another terminal is connected to terminal D.

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$\Large\bold\star\underline{\underline\textbf{How it works\:}}$

» First close the key K and adjust the value of resistance box for a suitable resistance R.

» Move the jockey on the wire till the galvanometer gives zero deflection.

» Note the length AB.
(Also note the length BC of the wire).

→ Let AB = l , BC = 100 - l

→ Now , according to the weightstone bridge principle,

P / Q = R / S

→ Where,

» P = resistance of the length ( l ) of the wire = lr

» Q = resistance of the length ( 100-l ) of the wire = ( 100-l ) r

r = resistance per unit length of the wire.

→ So ,
lr / ( 100-l ) r = R / S

→ S = ( 100- l / l ) x R

Hope it helped u.

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