Why should a voltmeter have a high resistance and a low current carrying capacity?

Explanation

Voltmeter is a high resistance galvanometer. It is used to measure potential difference between two points of the circuit. To measure a potential difference between two points of a circuit, the voltmeter is connected in parallel to the circuit across those two points. The potential difference between those two points will not be affected if there is no change in the current flowing through the circuit between those two point, which will be so if practically no current flows through voltmeter. The same is possible if voltmeter has a high resistance and a low current carrying capacity. That is why a voltmeter should have high resistance and low current capacity.