Resistance

Key Idea: The given circuit is a balanced Wheatstone bridge.
The equivalent circuit is shown below:

In the given circuit, the ratio of resistances in the opposite arms is same


Hence, bridge is balanced.
The given circuit now reduces to

Here, and resistors are in series, therefore

Now, the two resistors are connected in parallel, hence equivalent resistance is

Pure silver has the highest thermal conductivity of any metal. The resistivity of silver is about at it is lowest of all metal.

Electric circuit diagram of ammeter, galvanometer and voltmeter is shown below, Ammeter

Galvanometer

Voltmeter

Hence, the order of resistances So, the maximum resistance device is voltmeter.