Question

which of the following is true when connecting an ohmmeter to a circuit to measure the resistance of a circuit component?

the ohmmeter is connected in series with the circuit component to be measured.

the ohmmeter is connected in parallel to energized electrical components to read their resistance value.

the ohmmeter is connected in both series and parallel to the circuit component.

the circuit must be de - energized to measure resistance.

Explanation:

• For the first option: An ohmmeter has its own internal battery to provide current for resistance measurement. When measuring a component, the ohmmeter is connected in parallel (not series) with the component (after the circuit is de - energized). So this option is wrong.
• For the second option: If the electrical components are energized (have external power), connecting an ohmmeter (which has its own battery) in parallel will cause a conflict in current paths and may damage the ohmmeter or give incorrect readings. Also, the correct connection is parallel to the de - energized component, not energized. So this option is wrong.
• For the third option: An ohmmeter is connected only in parallel (after de - energizing the circuit) to the component whose resistance is to be measured, not in both series and parallel. So this option is wrong.
• For the fourth option: The circuit must be de - energized (disconnected from external power sources) when measuring resistance with an ohmmeter. This is because the ohmmeter has its own internal battery to supply the current for measuring the resistance of the component. If the circuit is energized, the external voltage and current will interfere with the ohmmeter's internal circuit and give incorrect readings or damage the ohmmeter. So this option is correct.

Answer:

D. The circuit must be de - energized to measure resistance.