What is the purpose of a series multiplier resistor used with a voltmeter?

The purpose of a series multiplier resistor used with a voltmeter is to increase the voltage-indicating range of the voltmeter. When you add a series multiplier resistor to a voltmeter, it allows the device to measure higher voltages than it could by itself. This is accomplished by dividing the voltage across the resistor and the voltmeter, effectively dropping the voltage that the voltmeter sees, which enables it to measure a larger voltage input without exceeding its internal limits.

In practical terms, when a higher voltage is applied to the circuit, the series resistor limits the current flowing through the voltmeter itself, ensuring that the voltmeter can safely measure the voltage without damage. This method allows for greater versatility in testing and measurement, as it makes the voltmeter suitable for a wider range of applications and voltage levels.