Electrical Circuits

Simple Electrical Circuits
Electricity will only flow in a complete circuit.


The bulb is connected in a circuit to a battery using two wires.


Electricity will not flow if the circuit is not complete .

Look carefully at the drawing and decide why the circuit is not complete.

If you were going to describe an electric circuit to someone, it is likely that you would want to draw it.

If you connected a bulb, battery and a switch, the circuit drawing might look like this:







It takes time to draw such a circuit and because people might draw batteries and bulbs etc. in different ways it could be very confusing.

It is easier if people use the same symbols in a circuit diagram.

Some Electrical Symbols


a connecting wire


a bulb

a switch

a battery


a motor

a buzzer

A Simple Circuit and its Symbols
Now if you were to draw the previous electrical circuit using the symbols it would look like this:




The original circuit using, battery, switch and bulb looked like this:

Batteries and Bulbs
You need the following:
Wire



Bulb

Bulb holder

Battery




Examine the battery. Write down as many things about it that you can.

Draw and label a picture of the battery in your notebook.



1. Try to get the bulb to light using the wire, bulb and battery.
2. Try to get the bulb to light using the wire, bulb, bulbholder and battery.
The bulb will only light if it is connected to the battery in an Electric Circuit.
A Current flows round the circuit.

To get your bulb to light, you should have set your materials like this:





Now unscrew the bulb from the bulb holder and look at it closely. The thin wire is called the filament.





What happens to the filament when you put the bulb back into the electrical circuit?





Write about your experiments and draw circuit diagrams to show how you set up the circuits.

1. Make an electrical circuit.
You will need: 4.5v batteryBulb and bulb holder4 paper clipsCovered copper wire
Scrape the covering off the ends of a 30cm length of wire. Twist one end round a paper clip. Do the same with another 30 cm length of wire and another clip.Fasten the clips to the terminals of the battery. Press the free ends of the wire to the bulb.
See what happens.
You have made a simple electric circuit.
Now screw the free ends of the wires to the terminals on the bulb holder and screw in the bulb.
Cut through one of the wires.
See what happens.
Scrape the covering off the ends of the wire you have just cut.
Twist each of these round a paper clip and press the two clips together.
See what happens.
What happens when you release your clips?
See if you can write about what happens and why.
2. Make an electrical conductor tester.
You will need: 4.5v batteryBulb and bulb holder4 paper clipsCovered copper wire
First make an electric circuit similar to the one you have just made.
Leave a small gap between the two paper clips which make up the switch.
Place an iron nail across the gap so that it touches both of the clips.See what happens.
Does the nail conduct electricity?
Test other materials to see if they are conductors or non-conductors of electricity e.g. pin, pencil, hair clip, scissors, straw, silver paper, coin, rubber band, various metals, paper clip.

Materials which can carry electric current are known as CONDUCTORS OF ELECTRICITY

Materials which cannot carry electric current are known as NON-CONDUCTORS OF ELECTRICITYOR INSULATORS


Metals are conductors.

Most non-metals are non-conductors.
Graphite and some liquids and solutions are non-metals but can conduct electricity.