Question

give the different makes of ammeter, voltmeter and laboratory.

Answer 1

Voltmeter is used to measure the potential difference across a load.So the resistance of the voltmeter shall be very high compared to circuit resistance.In contrast to this, if the voltmeter resistance is small, and connecting the voltmeter across load will be equal to parallel connecting another load.Then the circuit conditions are changed very much and no worth-while reading will be measured.So the resistance of voltmeter must be very high.If the meter's moving system has only a small resistance, additional resistance will be included in series with the moving coil.This additional resistance is known as swamping resistance.



An ammeter is used to measure the current flows through the circuit.So the resistance must be very small.If the ammeter resistance is very high, it will introduce high resistance in series with the existing circuit an disturb the circuit conditions.Ammeter should never connect across a load or voltage source