When the bar is depressed against spring tension, it forms a circuit and allows electricity to flow.

The tracking mechanism allows electricity to be produced during the day whenever the sun is more than 5 above the horizon.

When the blade's steel and pencil's lead come in contact with each other they will only allow electricity to go in one direction.

That allows 4 percent more electricity to be produced from the same amount of coal.

Other states also allow electricity, firing squads, hanging and lethal gas.

Along with the automobile, they reject most modern conveniences, while allowing electricity in their homes.

It acts like a gate or a valve, allowing electricity to go in one direction, but not the other.

This allows electricity to travel from one part to another, which is essential for the board to work.

A push to make switch allows electricity to flow between its two contacts when held in.

This trips the switch and opens the contacts that allow electricity to flow.