To carry out an R1+R2 continuity test on a lighting circuit, which steps are correct?

• A. Put a permanent link across live and neutral; set tester to high ohms; test between live and earth.
• B. Connect tester between live and earth at ceiling rose; set tester to low ohms; place temporary link between line and earth.
• C. Put in temporary link between line and earth; set tester to low ohms; then test between live and earth at the ceiling rose.
• D. Do not use a link; set tester to current mode; test between live and earth.

Answer: (C)

The test checks that the live and earth conductors form a continuous path along the lighting circuit, so the tester’s current can travel from live through the circuit (R1) and back via the earth path (R2). To do this properly, you create a temporary link between line and earth at the origin of the circuit, then use a low resistance range on the tester and measure between live and earth at the ceiling rose. With the link in place, the test current has a return path through both conductors, so the reading reflects the combined R1 and R2 values for the entire run. Testing at the ceiling rose ensures the entire circuit is included in the measurement. Not using a link would leave no return path for the test current, and using high ohms or current-mode would not give a valid continuity reading for R1+R2.