electric current = flow of electrons

In the last section we learned how electric flow happens. Let’s think about this some more. If you rub your shoes on the carpet and then touch a doorknob, you may feel a shock. You may see a spark. This is because you picked up electrons on your body by rubbing the carpet. You got a negative charge. The doorknob is metal. It is a good conductor. Electrons flow between your hand and the doorknob. This is called an electric current.

In an Electric Circuit, electrons flow towards a place in the circuit where there is a positive charge. This is because negatively charged particles are attracted to positively charged particles. The flow of electrons will continue so long as the source of electrons has energy and so long as there is a conductor through which the electrons can flow.

As long as there are conductor atoms, the current will keep going. But let’s imagine that an atom gets an extra electron and there are no conductor atoms nearby. The atom cannot give away its extra electron. The current must stop.

How can you keep a current going?

If the conductor that you are using for your circuit has ends to it, the flow of electrons cannot continue because they will reach a place where there is nowhere for them to do. (You can try this out when you are ready to build circuits). But if you join the line and make a circle, there is no end. The electricity can keep moving.

The circle we just described is called a circuit. A circuit is the path an electric current takes as it flows.

Have you ever used a battery? A battery stores electrical energy. It pushes electrons into the wire. This gets the flow of electrons started. The amount of force a battery has to push electrons is measured in volts.

Most batteries for flashlights and toys have a force of about 1.5 volts. This is very little force. The number of volts from a wall socket is 120 volts. That is enough force to give a very bad electric shock. It can hurt a person or kill them. Never experiment with the current from wall sockets.

Never work with electricity alone. Always make sure a teacher or parent is watching. Wait for directions from your teacher or parent before you begin to work. Electricity can be very dangerous, though you are very unlikely to be hurt using the batteries provided in elementary classrooms.

This is a picture of a simple circuit. A simple circuit is a simple closed loop, or a closed circuit. The circuit will not work if there is a break in the loop. It will not work if it is attached to an insulator, like wood, paper, or plastic.

Look at the wire that connects each part of the circuit. The wire is metal. A copper wire is a good conductor. Many times copper wires are covered with rubber or plastic. Rubber and plastic are good insulators. The covering will protect us from electric shocks.

There are four parts to this circuit:

1. The battery is the energy source.

2. The wire is the conductor.

3. The light bulb receives the energy.

4. The switch.

Now look at the fourth part. It is a switch. If you push down on the metal lever of the switch, it will touch the other metal part. This will complete the circuit. The light bulb will light up.

If you do not push the metal lever down, the circuit is not complete. The light bulb will not light up.

Now think about light switches in your house. If you turn them off, you are breaking the circuit. If you turn them on, you are completing the circuit. On/off switches help people control electricity.

Video Instruction
*Availability of You Tube video links may vary. eTAP has no control of these materials.

• Physical Science 6.2a - Simple Circuits [7:48]

• Simple Pulse Circuit with Air Core Coil [3:47]

Now let's do Practice Exercise 1-2 (top). Choose printer friendly or online exercises. Printer friendly version requires the Adobe Acrobat Reader 5. Click HERE to obtain a free copy.