How can an electrician determine if a wire is live?

An electrician can determine if a wire is live by using a voltage tester or multimeter to check for electrical current. This method is reliable and safe, providing a direct measurement of voltage present in the wire. A voltage tester or multimeter is designed to measure electrical parameters, ensuring that whether or not the wire is carrying current can be accurately assessed. This is critical for safety, as it helps avoid electric shock during electrical work.

The other options, while they may seem plausible at first glance, are less reliable or safe. Feeling for heat on the wire can indicate a problem but is not a definitive way to determine if a wire is live, as a wire could be energized without being hot. Visual inspection may reveal issues like wear or damage to the insulation but does not provide any information about the electrical state of the wire itself. Using a circuit breaker reset tool does not measure live current; rather, it is used to reset a tripped breaker, which does not confirm live wires.