To check if a rheostat is working properly, test each tap for a different resistor value using which instrument?

• A. DMM
• B. Oscilloscope
• C. Power supply
• D. LCR meter

Answer: (A)

A digital multimeter is the best tool for this. To verify a rheostat, set the DMM to resistance (ohms) mode and measure from the common end of the resistor to each tap in turn. This gives you the exact resistance value for every segment, showing that each tap provides a different, expected value as the wiper moves along the track.

This direct resistance reading is exactly what you need; an oscilloscope shows voltage or waveform, not the static resistance. A power supply is a source of power, not a meter. An LCR meter can measure resistance in some setups, but it’s more than what’s needed for a straightforward check of a rheostat’s taps, and a DMM is the standard, simpler choice.

Tip: disconnect power and measure the resistor values with the circuit open. If the readings don’t match the expected step changes, the track or taps may be faulty.