Electrical Circuits

• The source of electricity will have two terminals: a positive terminal and a negative terminal.

• The source of electricity (whether it is a generator, battery, etc.) will want to push electrons out of its negative terminal at a certain voltage. For example, a AA battery typically wants to push electrons out at 1.5 volts.

• The electrons will need to flow from the negative terminal to the positive terminal through a copper wire or some other conductor. When there is a path that goes from the negative to the positive terminal, you have a circuit, and electrons can flow through the wire.

• You can attach a load of any type (a light bulb, a motor, a TV, etc.) in the middle of the circuit. The source of electricity will power the load, and the load will do its thing (create light, spin a shaft, generate moving pictures, etc.).

Electrical circuits can get quite complex. But at the simplest level, you always have the source of electricity (a battery, etc.), a load (a light bulb, motor, etc.), and two wires to carry electricity between the battery and the load. Electrons move from the source, through the load and back to the source.

Moving electrons have energy. As the electrons move from one point to another, they can do work. In an incandescent light bulb, for example, the energy of the electrons is used to create heat, and the heat in turn creates light. In an electric motor, the energy in the electrons creates a magnetic field, and this field can interact with other magnets (through magnetic attraction and repulsion) to create motion. Each electrical appliance harnesses the energy of electrons in some way to create a useful side effect.

What About Lightning? Photo courtesy NASA If air is an insulator, then how can a bolt of lighting flash from a cloud to the ground through non-conducting material? In the case of lightning, there is so much electrical energy stored up between the cloud and the ground that, eventually, the energy is able to rip the electrons off the atoms in the air. Once this ripping process starts, the air becomes a plasma (a separate state of matter where there are lots of free electrons created by heat or high voltage -- see How Plasma Cutters Work to learn about this state). Once it turns to plasma, the air can easily conduct electricity with the free electrons, and the bolt of lightning shoots to the ground through the plasma conductor. This same process allows a spark to flow between the conductors of a spark plug or a stun gun, and also carries electricity from one end to the other of a fluorescent tube.

Now that we know what electricity is and how it works on a basic level, let's learn more about some of the concepts associated with it, like voltage, current and resistance.