Question

In a meter bridge setup, which of the following should be the properties of the one-meter-long wire?
(A) High resistivity and low temperature coefficient
(B) Low resistivity and low temperature coefficient
(C) Low resistivity and high temperature coefficient
(D) High resistivity and high temperature coefficient

Answer 1

Hint: We only need to apply the resistance concept on the following circuit. Also, it should be observed how high or low resistivity will affect the meter bridge.
Formula used: As required here we need resistance formula:
$R = \rho \dfrac{l}{a}$
Here, $R$ is the resistance.
$\rho $ is the resistivity of the wire.
$l,a$ are the length and area of the wire.

Complete step by step answer:
We know that a meter bridge length should be constant.
So, low temperature coefficient is required.
Here,
$R = \rho \dfrac{l}{a}$
So, for constant $l,a$ there will be:
$R \propto \rho $
Then, for higher value of resistance for a small displacement along wire we are getting more deflection.
So, for high resistivity our device is much more sensible.

Thus, the correct option is A.

Additional Information : A meter bridge also called a slide wire bridge is an instrument that works on the principle of a Wheatstone bridge. A meter bridge is used in finding the unknown resistance of a conductor as that of in a Wheatstone bridge. The Wheatstone Bridge was originally developed by Charles Wheatstone to measure unknown resistance values and as a means of calibrating measuring instruments, voltmeters, ammeters, etc, by the use of a long resistive slide wire.

Note: The reason why this bridge is called the Meter Bridge is because of the fact that it works on the Wheatstone bridge's principle. So, people also popularly call it as Whetstone’s meter bridge. Another thing is that the wire length used in this circuit is of 1 meter, so it has got its name as a meter bridge. The meter bridge uses the same principle as the Wheatstone Bridge. It is used to find the unknown Resistance of the Material. The meter bridge consists of a wire of 100 cm, a scale, one unknown Resistor, one known Resistor or a Resistance Box, a Galvanometer and a jockey.