Question

Why should an ideal voltmeter have infinite resistance, and an ideal ammeter has no resistance?

Answer 1

Step 1: Voltmeter

1. Voltmeter is a device used to measure potential difference across two points and is connected in parallel.
2. An ideal voltmeter should have infinite resistance because to measure the potential difference all the current should pass through the resistor and no current should pass through voltmeter for precise readings. Because for infinite resistance the flow of current is zero.

Step 2: Ammeter

1. Ammeter is device used to measure current and is connected in series.
2. To measured accurate current, there must be no change in current of the circuit by the use of ammeter in series of circuit.
3. This is possible only when ammeter has no resistance.

Hence, An ideal voltmeter have infinite resistance, and an ideal ammeter has no resistance for accurate measurement of potential difference and current.