What should always be done just before you work on an electrical circuit (touching components):

• A. Check amperage with a good meter.
• B. Check voltage with a good meter.
• C. Look to make sure switch is down.
• D. Turn power on.

Answer: (B)

The key idea is to ensure the circuit is not energized before you touch any components. The safest first check is to verify there is no voltage present by using a properly rated meter. This directly confirms whether the circuit could deliver a shock, even if you think a switch is off or the power is “down.” Relying on a switch position alone isn’t reliable, and turning the power on would be dangerous.

Why the other ideas aren’t sufficient: checking amperage isn’t a good indicator of live status because current only exists when the circuit is energized and you’d have to have a live path to measure it; you could miss a live conductor or a backfed source. Simply looking at a switch doesn’t guarantee there’s no voltage somewhere in the circuit. Turning the power on is the opposite of safe practice when you’re about to work on the circuit.

So, the best approach before touching anything is to de-energize if possible, then use a good meter to check for the presence of voltage.