3-7 Simple Circuits

You know that when charged particles build up in an object it is called static electricity.  Another kind of electricity occurs when electrons flow in a current.  A battery and wires can make current flow.

Look at the simple electric circuit below.  It consists of four parts 1.) a battery, 2.) a switch, 3.) a light bulb, 4.) a wire.

The battery pushes electrons from the negative terminal (where there are many electrons), through the switch, the light bulb, and the wire into the positive terminal (where there are not many electrons).  As electrons pass through the wire and into the light bulb, a special kind of wire inside the bulb, called a filament, lights the bulb.  Have you ever heard a light bulb pop when it burns out?  The filament has broken and the flow of electrons has been interrupted.

What if you want to turn the light bulb off?  You need to stop the flow of electrons.  Look at the simple circuit.  Notice the switch is off.  The circuit has been broken.  The light bulb is not lit.  The flow of electrons has stopped because there is a gap in the circuit, and the electrons no longer have a closed path.  If you want to turn the light bulb back on, the switch must be closed to complete the circuit.

The wire used in electric circuits is usually made of copper.  Copper and silver are good conductors.  Conductors carry electrons very easily.

Rubber, plastic, and glass are good insulators.  Insulators do not permit electrons to flow through them.  Insulators are poor conductors of electricity and are therefore used to cover wires used in circuits.

Directions: Answer the questions about electricity.  Use the illustrations to help you.

The negative terminal of the battery has many .

The battery pushes electrons from the negative terminal  through the switch, the light bulb, and the wire into the terminal (where there are not many electrons).

A special kind of wire inside a light bulb is called a .

carry electrons very easily.

Which of the following is a good conductor?

copper wire
glass

do not permit electrons to flow through them.

Which of the following is a good insulator?

silver
plastic