# Simple question regarding the ideal voltage in an ammeter and a voltmeter

So this question came up as was revising past paper questions for the IB Physics exam.

While I understand that the resistance in an ideal ammeter is supposed to be zero as you're trying to measure the current without anything affecting it such as resistance, I was wondering why the resistance of an ideal voltmeter is better being infinite.

The answer to the question was B, by the way.

To measure the potential difference accross a component with a voltmeter, you need to connect the voltmeter in parallel with the component. Then the current can either flow accross the component (say a resistor) or accross the voltmeter. Since current is conserved ($I_{in} = I_{out}$) at a junction, the total current in will be the sum of the current that passes through the resistor and through the voltmeter.