Question 6A520

A voltmeter uses a sensitive current-measuring meter movement internally. To measure voltage, a resistor, known as a multiplier resistance, is placed in series with this movement. The purpose of this series multiplier resistance is to drop a significant portion of the voltage being measured, allowing only a small, proportional current to flow through the meter movement. By increasing the total resistance in the circuit (the meter movement's resistance plus the multiplier resistance), a higher voltage is required across the combination to produce the full-scale deflection current for the meter. This effectively extends the voltage range that the voltmeter can safely and accurately indicate. Therefore, option B is correct because adding series resistance increases the total resistance, which, by Ohm's Law (V=IR), means a higher voltage can be applied across the circuit for the same full-scale current, thus increasing the measuring range. Option A is incorrect as multiplier resistances are fundamental to voltmeter design. Option C is incorrect as it describes the opposite effect; adding resistance increases the range, it does not decrease it.