Electrons in a circuit
An atom of helium showing the relative positions of the electrons (black) and the protons (red). All matter is made up of atoms. Each atom has positive charges(protons) in its center(nucleus) and negative charges(electrons) orbiting the nucleus. See the simple animation on the left. Protons are colored red, electrons are black while neutrons are blue. Neutrons are neutral particles that pack into the center of the atom along with the protons.
Atoms tend to keep a tight hold on their electrons through strong attraction between the protons(positive) and the electrons.

Metal atoms however, find it difficult to hold all their electrons and always tend to allow one or two of them to move from atom to atom. These free electrons are what makes metals such good conductors.

Electrons in a wire travel at about 2-3 million kilometers an hour, at room temperature. This is very fast indeed but does not produce a current because their motion is random. There is no overall flow in any particular direction.

But when a battery is connected across the wire the electrons are forced to move in one direction producing a current.

As the electrons gain speed they bump into the stationary metal atoms and transfer some of their kinetic energy (moving energy) into them. As the metal atoms absorb energy from the electrons they start to vibrate strongly and heat is generated. This is why a wire becomes hot when a current is passed through it.

The animation above is somewhat simplified showing electrons freely moving in one direction when a battery is connected. The reality is that frequent collisions between the electrons and atoms tend to slow the electron's overall speed through the wire to just 0.01cm/s. It would take roughly three hours for an electron to travel through one meter of wire.
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The elastic band provides the tension to automatically close the gate. Metal contacts that complete the circuit and cause the light to glow when the gate is shut The light indicating if the gate is open or closed An electromagnet that activates the lock The bolt that is lifted through a screw eye by the electromagnet The gate
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