How does an ohmmeter measure resistance?

• A. By sending a small amount of electrical current through the circuit
• B. By heating the circuit
• C. By measuring magnetic field around wires
• D. By counting electrons in a conductor

Answer: (A)

An ohmmeter determines resistance by pushing a small, known current through the component and watching the response so resistance can be calculated with Ohm’s law (R = V/I). By injecting that current, the meter measures either the voltage across the unknown resistance or the current that flows, and from those values it derives the resistance. This approach relies on injecting current; it’s not about heating the circuit (which shows power dissipation, not resistance), measuring magnetic fields (which indicate current or inductance), or counting electrons (not a practical way to gauge resistance). For accurate readings, ensure the circuit is de-energized before testing.