To convert a galvanometer to a voltmeter, a

Analyze the question: A galvanometer is a sensitive instrument that detects very small currents. To make it measure potential difference (voltage), we must modify it so it can handle larger voltages without too much current flowing through its coil.

Concept:

• A voltmeter is connected in parallel across a component, so it must have a very high resistance. This ensures it draws negligible current from the circuit and doesn't alter the voltage being measured.
• An ammeter is connected in series and must have a very low resistance. It is made by adding a low-resistance shunt in parallel with the galvanometer.

Solution:

1. A galvanometer has a small resistance G and a full-scale deflection current Ig.
2. To measure a voltage V, we add a large resistance R (called a multiplier) in series with the galvanometer.
3. The series resistor limits the current to Ig at the full-scale voltage:

V = Ig(G + R) → R = V/Ig − G

4. This gives the total resistance (G + R) a high value, which is exactly what a voltmeter needs.

Checking the options:

• A. High resistance in series: Correct. This is the multiplier method.
• B. High resistance in parallel: Wrong. A parallel resistor would not limit the current through the galvanometer coil, and the combined resistance would be lower than G.
• C. Low resistance in parallel: This is the ammeter conversion (shunt).
• D. Low resistance in series: Wrong. It would not give the high total resistance a voltmeter needs.

Tip: Remember "VHS, ALP":

• Voltmeter = High resistance in Series
• Ammeter = Low resistance in Parallel (shunt)