FCC Exam Question: 3-74L4

What is the purpose of a shunt resistor used with an ammeter?

A. A shunt resistor is not used with an ammeter.
B.
C. It is used to increase the ampere indicating range of the ammeter.
D. It is used to increase the voltage indicating range of the voltmeter, not the ammeter.
Correct Answer: C

Explanation: A shunt resistor is connected in parallel with an ammeter's internal meter movement. Its purpose is to divert, or "shunt," a portion of the total current flowing through the circuit away from the sensitive internal coil of the ammeter. By allowing only a calibrated fraction of the current to pass through the meter movement, the ammeter can safely measure much larger currents than its internal mechanism is designed for, thereby increasing its overall ampere indicating range. Option A is incorrect because shunt resistors are indeed commonly used with ammeters. Option D describes the function of a *multiplier* resistor used in *series* with a *voltmeter* to increase its voltage range, which is a different application for a different type of meter.

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Includes Elements 1, 3, 6, 7R, 8, and 9.