Which test measures insulation resistance between conductors or to ground?

• A. Continuity test.
• B. Voltage test.
• C. Insulation resistance test.
• D. Oscilloscope test.

Answer: (C)

Insulation resistance testing focuses on how well the insulation resists leakage current between conductors or to ground. By applying a high DC voltage with a megohmmeter, you measure leakage as a resistance value; a higher resistance indicates better insulation integrity, while a lower value signals deterioration, moisture, or contamination. This directly assesses insulation quality. In contrast, a continuity test checks for a complete conductive path to confirm wiring connections; a voltage test applies a high voltage to verify insulation can withstand voltage or to test operation, not to quantify leakage resistance; and an oscilloscope test observes waveform shapes to analyze signal behavior rather than insulating properties.