A voltmeter has a resistance G and range V . Calculate the resistance to be used in series with

step 1 Hi in the given problem resistance of the volt meter coil of the volt meter is given as G capita

A voltmeter has a resistance G and range V . Calculate the...

Key Concepts

Meter Internal Resistance

An analog voltmeter is designed with a high internal resistance to minimize the loading effect on the circuit being measured. The internal resistance is a critical parameter because it determines how much current the meter draws and affects the accuracy of the voltage measurement. In the context of range extension, knowing the meter’s internal resistance is essential to ensure that it only receives a safe, full-scale voltage while a resistor is used to drop the excess voltage.

Series Resistor (Multiplier Resistor)

To extend the measurement range of a voltmeter beyond its inherent limit, a resistor is added in series with the meter. This additional resistor, often called a multiplier resistor, drops the difference in voltage between the new maximum measurement and the full-scale reading of the meter. By selecting the correct resistor value, the meter only experiences its rated voltage, while the series resistor absorbs the remaining voltage, thereby linearly scaling the measurement.

Voltage Divider Principle

The extension of a voltmeter’s range using a series resistor relies on the voltage divider principle. In a series circuit, the voltage across each resistor is proportional to its resistance value. By designing the circuit so that the full-scale voltage of the meter occurs when a specified overall voltage is applied, the voltage divider equation can be used to determine the appropriate value for the series resistor. This ensures that the meter shows an accurate reading even for voltages exceeding its normal range.

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