What is one essential safety measure when working on live circuits?

Using rubber gloves is an essential safety measure when working on live circuits because they provide electrical insulation, significantly reducing the risk of electrical shock. Rubber is a poor conductor of electricity, which helps prevent current from passing through the worker's body if they accidentally come into contact with a live conductor. This protective gear is crucial when handling any live electrical components, as the gloves act as a barrier and protect against the potential for serious injuries or fatalities caused by electric currents.

The other options, while important for general safety, do not specifically address the risks associated with working on live circuits. Increased lighting helps improve visibility, which is beneficial but does not protect against electrical hazards. Safety goggles are important to protect the eyes from flying debris or sparks but do not provide any protection against electrical shock. Working at night may hinder visibility and increase the risk of accidents without adequate lighting and is not a recommended practice in electrical work without proper safety measures.