Question

A galvanometer acting as a voltmeter will have

• A. a high resistance in series with its coil
• B. a low resistance in parallel with its coil
• C. a low resistance in series with its coil
• D. a high resistance in parallel with its coil

Answer 1

The Correct Option is A

To convert a galvanometer into a voltmeter, we need to modify its resistance characteristics. Let's explore why a high resistance in series with the galvanometer's coil is required for it to function as a voltmeter.

Understanding the Galvanometer:

A galvanometer is a device used for detecting small electrical currents. It has a coil through which current flows, causing a needle to deflect. This deflection is proportional to the current passing through the coil. A galvanometer is very sensitive and can only handle small currents.

Converting to a Voltmeter:

To use a galvanometer as a voltmeter, which measures potential difference (voltage) across two points, the current through the galvanometer must be minimized while still allowing for a measurable deflection. This is because a voltmeter needs to measure voltage without significantly affecting the current in the circuit.

High Resistance in Series:

1. Adding a high resistance in series with the galvanometer limits the total current passing through it. This ensures that the galvanometer can safely measure higher potential differences without receiving too much current.
2. The high series resistance allows the voltmeter to have minimal impact on the circuit's overall current flow. This low impact is critical because the primary purpose of a voltmeter is to measure voltage while not altering the circuit conditions significantly.

Why the Other Options are Incorrect:

• Low resistance in parallel: This configuration is used in ammeters, not voltmeters. It allows for a larger current to bypass the galvanometer, reducing the current through the coil.
• Low resistance in series: This would mean more current flows through the galvanometer, which could damage it if the voltage is high.
• High resistance in parallel: This would not effectively limit the current flowing through the galvanometer itself, which a voltmeter requires.

Conclusion:

Therefore, the correct answer is that a galvanometer acting as a voltmeter will have a high resistance in series with its coil to safely measure potential difference without drawing excessive current.