What is the ideal resistance for the ammeter in the circuit

What is the ideal resistance for the ammeter in the circuit below? What is the ideal resistance for the voltmeter in the circuit below? Assuming we have a balanced Wheatstone bridge what is the current measured by the ammeter? What is the value of the unknown resistance Rx in this situation?

Solution

The ideal resistance of an ammeter is zero.

The ideal resistance of a voltmeter is infinite.

For balanced wheat stone bridge the current measured by the ammeter is zero.

R₁R_X=R₂R₃

=> R_X=(R₂R₃)/R₁