Question

A Galvanometer converted into voltmeter by connecting :

• A. Low resistance parallel
• B. Low resistance series
• C. High resistance parallel
• D. High resistance series

Answer 1

Answer:

D. High resistance series

• A Galvanometer is a sensitive device used to detect small electric currents. To convert it into a Voltmeter, which measures the potential difference (voltage) across two points, specific modifications are required.

• Circuit Configuration: To function as a voltmeter, a high resistance (often denoted as R) must be connected in series with the galvanometer coil.

• Purpose of High Resistance: The primary goal of adding high resistance is to increase the total resistance of the device. This ensures that the voltmeter draws a negligible amount of current from the circuit it is measuring, thereby minimizing the error in the voltage reading.

• Ideal Voltmeter: An ideal voltmeter should have infinite resistance so that it does not draw any current from the circuit, effectively maintaining the potential difference as it was before the connection.

• Formula: The relationship is given by V = I_g (R + G), where:

  • V is the maximum voltage range to be measured.

  • I_g is the full-scale deflection current of the galvanometer.

  • R is the external series resistance.

  • G is the internal resistance of the galvanometer.

• converting a galvanometer into an ammeter requires connecting a low resistance (shunt) in parallel, which is the exact opposite of the voltmeter conversion method.