Question

Which of the following instruments has the highest internal resistance ?
1. Ammeter
2. Galvanometer
3. Voltmeter
4. Milliammeter

Answer 1

Correct Answer - Option 3 : Voltmeter

CONCEPT:

Measuring instruments are:

Properties	Ammeter	Galvanometer	Voltmeter	Milliammeter
Measures	It is a device used to measure current and is always connected in series with the ‘element’ through which current is to be measured.	An instrument used to detect, measure, and determine the direction of electric currents is called a galvanometer.	It is a device used to measure potential difference and is always put in parallel with the ‘circuit element’ across which potential difference is to be measured.	Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters.
Resistance value	The ideal resistance of the ammeter is zero	A resistance of high value is connected in series to convert the galvanometer into a voltmeter.	A voltmeter is said to be ideal if its resistance is infinite, i.e., it draws no current from the circuit element for its operation.

EXPLANATION:

• From the above table, it is clear that Voltmeter is the instrument that has the highest internal resistance. Therefore option 3 is correct.