Engineer's Asylum

Ideal voltmeter and ideal ammeter problem


Hi all
Does anybody know why an ideal voltmeter has infinite resistance while that of ideal ammeter have no resistance? Can anyone explain the concept behind it?



An ammeter is always connected in series with the circuit, as a result, all the current flow through it without any problem. If there is non-zero resistance in ammeter, there will be a potential difference across its ends and the actual potential difference for the circuit will be lower than the supplied. To overcome this problem, its resistance should be zero.

A voltmeter is always connected in parallel with the original circuit. If it draws any current from the main circuit, the actual potential difference in the main circuit may not be determined. So, no current should be able to pass through the voltmeter. Thus, it’s resistance should be infinity.

Although, the “Ideal” ammeter and voltmeter concepts are theoretical concepts. They are not going to work in practical scenarios.


What will happen if I try to connect an ammeter in parallel with an element? Do you think such an arrangement will work?