Question:medium
A galvanometer is converted into a voltmeter by connecting ________.
A galvanometer is converted into a voltmeter by connecting ________.
Show Hint
Ammeter: Low resistance in parallel (Shunt); Voltmeter: High resistance in series.
Updated On: Jun 26, 2026
- a high resistance in series
- a low resistance in series
- a high resistance in parallel
- a low resistance in parallel
- an inductance in series
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept
This question asks about the modification required to convert a galvanometer into a voltmeter.
- A galvanometer is a sensitive device that detects small electric currents. It has a low internal resistance and gives a full-scale deflection for a very small current (\(I_g\)).
- A voltmeter is an instrument used to measure the potential difference (voltage) between two points in a circuit. An ideal voltmeter should have a very high resistance so that it draws a negligible current from the main circuit, thus not altering the voltage it is intended to measure.
Step 2: Detailed Explanation
To convert a galvanometer into a voltmeter, we need to achieve two things:
1. Increase its overall resistance to make it behave like a good voltmeter.
2. Extend its range, so that it can measure voltages much larger than the small voltage that causes its full-scale deflection (\(V_g = I_g R_g\)).
To achieve this, a very high resistance, called a "multiplier resistance" (\(R_s\)), is connected in series with the galvanometer.
- Series Connection: Connecting the high resistance in series adds it to the galvanometer's resistance, significantly increasing the total resistance of the instrument (\(R_V = R_g + R_s\)). This satisfies the high-resistance requirement of a voltmeter.
- Range Extension: The high series resistance limits the current flowing through the galvanometer. If we want to measure a voltage \(V\) (where \(V>V_g\)), most of this voltage will drop across the high series resistor, ensuring that the current through the galvanometer does not exceed its full-scale deflection current \(I_g\). The value of \(R_s\) is chosen based on the desired voltage range: \(V = I_g (R_g + R_s)\).
Connecting a resistance in parallel would decrease the overall resistance, which is the procedure for converting a galvanometer into an ammeter.
Step 4: Final Answer
A galvanometer is converted into a voltmeter by connecting a high resistance in series with it.
This question asks about the modification required to convert a galvanometer into a voltmeter.
- A galvanometer is a sensitive device that detects small electric currents. It has a low internal resistance and gives a full-scale deflection for a very small current (\(I_g\)).
- A voltmeter is an instrument used to measure the potential difference (voltage) between two points in a circuit. An ideal voltmeter should have a very high resistance so that it draws a negligible current from the main circuit, thus not altering the voltage it is intended to measure.
Step 2: Detailed Explanation
To convert a galvanometer into a voltmeter, we need to achieve two things:
1. Increase its overall resistance to make it behave like a good voltmeter.
2. Extend its range, so that it can measure voltages much larger than the small voltage that causes its full-scale deflection (\(V_g = I_g R_g\)).
To achieve this, a very high resistance, called a "multiplier resistance" (\(R_s\)), is connected in series with the galvanometer.
- Series Connection: Connecting the high resistance in series adds it to the galvanometer's resistance, significantly increasing the total resistance of the instrument (\(R_V = R_g + R_s\)). This satisfies the high-resistance requirement of a voltmeter.
- Range Extension: The high series resistance limits the current flowing through the galvanometer. If we want to measure a voltage \(V\) (where \(V>V_g\)), most of this voltage will drop across the high series resistor, ensuring that the current through the galvanometer does not exceed its full-scale deflection current \(I_g\). The value of \(R_s\) is chosen based on the desired voltage range: \(V = I_g (R_g + R_s)\).
Connecting a resistance in parallel would decrease the overall resistance, which is the procedure for converting a galvanometer into an ammeter.
Step 4: Final Answer
A galvanometer is converted into a voltmeter by connecting a high resistance in series with it.
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