In a potentiometer, a high resistance is connected in series with a galvanometer for several reasons. Firstly, the galvanometer is a sensitive instrument that responds to small currents. By adding a high resistance in series, typically called a shunt resistor, the current through the galvanometer is limited, preventing it from being damaged by excessive current. This setup ensures that the galvanometer operates within its safe current range, thereby protecting its delicate mechanism and ensuring accurate readings.
The high resistance in series with the galvanometer also serves to reduce the impact of the galvanometer’s own resistance on the circuit being measured. Galvanometers typically have a finite resistance, and if connected directly, they could alter the voltage or current being measured. By adding a high resistance in series, the overall resistance in the circuit is increased, minimizing the disturbance caused by the galvanometer’s internal resistance.
In the context of converting a galvanometer into a voltmeter, a high resistance is similarly added in series with the galvanometer to extend its measurement range. A voltmeter needs to measure a range of voltages without drawing significant current from the circuit under test. The high series resistance ensures that the voltmeter has a high input impedance, minimizing loading effects on the circuit and accurately measuring the voltage without significantly affecting the circuit’s behavior.
A galvanometer connected in series with a high resistance is often referred to as a “shunted galvanometer.” This configuration allows the galvanometer to measure currents or voltages without directly affecting the circuit’s operation, making it suitable for precise measurements in various applications such as in laboratory experiments, electrical testing, and calibration procedures.