If an analog voltmeter is connected to a 24 V DC circuit with the polarity reversed, what reading will occur?

• A. 0 or fewer volts
• B. 24 volts
• C. -24 volts
• D. Cannot determine

Answer: (A)

When a DC voltage source is applied with reversed polarity to an analog voltmeter, the meter would be driven in the opposite direction from how it’s calibrated. A standard analog voltmeter is scaled to display positive voltages on its visible dial, so a negative reading isn’t shown as a positive number. As a result, the observable indication is either no deflection (0 volts) or a negative indication that the scale cannot display as a positive value. In short, reversing the polarity yields 0 or a reading representing a negative voltage, not a positive 24 V.