Electricity is another form of energy. It is generated from various sources. It also has a wide range of uses.
During installation and use of electricity various tools and materials are used.
Look at the following pictures.
Describe each picture above.
Use the pictures to predict what you are going to learn.
15.1: importance of electricity
Activity 15.1: identifying the importance of electricity
The following picture shows the general importance of electricity.
Identify the uses indicated 1, 2, 3 and 4.
Electricity is important in the following ways. 1. It is used to power radios, televisions, computers and phones. 2. It is used to light homes, schools and other important places. 3. It is used to power vehicles and machines.
4. It is used for heating in ovens and microwaves.
5. It is used for air conditioning and refrigeration.
6. Used to press clothes (iron) and to dry clothes in dry cleaning shops.
7. Used to solder (press together) metals.
15.2: Production of electricity
Activity 15.2: Field trip to electricity producing plant
Visit an electricity producing plant.
What to do:
1. Observe how electricity is generated and supplied.
2. Ask questions about generation of electricity.
3. Make short notes in your notebook.
4. Go back to school and compare the notes that you wrote with those of your friends.
Electricity can be produced from its sources in different ways. Sources of electricity include:
Others are generators (diesel and petrol), water and fuel.
Bicycle dynamo A bicycle dynamo is a generator, which produces electrical energy when rotated by a bicycle wheel.
Activity 15.3: Producing electricity using a simple dynamo
Bicycle with dynamo and bulb.
What to do:
1. Obtain a bicycle with a dynamo and bulb installed.
2. Turn the bicycle upside down so that both wheels face up and its pedals are free.
3. Switch on the bulb when the bicycle wheels are not moving. What happens to the bulb?
4. Rotate the bicycle pedals slowly at first. Switch on the bulb and observe what happens.
5. Rotate the bicycle pedals very fast while the bulb is switched on. How does the bulb appear?
6. Allow the wheel to rotate until it stops. What happens to the bulb? What conclusion can you make from the experiment above? Compare your notes with others.
When the bicycle is at rest (wheels not moving). The bulb does not light up. When the pedals are rotated to make the wheels move, the bulb lights up.
When the wheels are rotated very fast, the bulb light gets brighter.
A bicycle dynamo generates electricity when the bicycle is being pedalled.
Solar panels come in different sizes and shapes depending on their use. The panels are usually placed where they can receive maximum sunlight.
A solar panel produces electricity by changing light energy from the sun to electricity.
The electricity produced can be stored in a car battery.
It is then used when there is no sunlight especially at night.
Activity 15.4: Producing electricity from simple solar panels
Simple solar panel e.g. a solar lamp or a solar powered mobile phone.
What to do:
(i) Obtain a solar lamp or a solar powered mobile phone.
(ii) Ensure that your phone or lamp does not have power
(iii) Switch on your phone or solar lamp. What do you observe?
(iv) Place your solar lamp or phone in the sun (30 minutes to 1 hour).
Ensure that the part having the solar cells faces the sun. What happens?
Observation When the solar lamp does not have power, it cannot light up.
After exposing the solar panel to the sun for some time, the solar lamp lights up.
A solar panel generates electricity when exposed to the sun.
Practice Activity 15.1
1. What is hydroelectric power.
2. What are the men in the picture doing.
3. Name 3 hydroelectric power-generating projects in our country.
15.3: Common tools used in electricity
Activity 15.5: identifying common tools used in electricity
Name the following tools used in electricity
What are the uses of the tools shown above.
15.4: Common materials used in electricity
Materials used in electricity are either conductors or insulators.
Activity 15.6: identifying common materials used in electricity
Name the following materials used in electricity.
(b) What are the uses of tools shown above?
Conductors can be used to make conducting wires, contacts in switches and fuses, plugs and sockets. Insulators are used to insulate electric cables and prevent short-circuiting.
15.5: Simple electric circuit
Activity 15.7: Making a simple electric circuit
• Dry cells
What to do:
1. Arrange the materials listed above as shown in the diagram.
2. Remove one end of the wire from the dry cell. What happens.
(i) Make other circuits by connecting two or more dry cells.
(ii) Connect positive terminals of dry cells to negative terminals as shown in the following example.
(iii) Make your observations. Note the brightness of the bulb when one dry cell is connected and
when two dry cells are connected.
An electric circuit is a path through which electricity flows.
The major parts of a simple electric circuit are:
(a) Source of electricity (dry cell or battery)
(b) Conducting wires
(c) A bulb A switch can be included in the set up. A switch is used start and stop electric flow in the circuit.
Practice Activity 15.2
Draw the picture shown below in your notebooks
Name the parts that you know.
Controlling an electric circuit
An electric circuit can be controlled by a switch. The switch helps to control the flow of electric current by switching it on or off. When you switch on, you complete the circuit. When you switch off, you break the circuit.
Activity 15.8: Controlling an Electric circuit
What to do:
1. Name the things in your homes and at school that use switches. List them down in your notebooks.
2. Make set-ups as shown below.
3. (a) Does the bulb light in Set-up A light? Write down reasons for your answer.
(b) Does the bulb light in Set-up B light? Write down reasons for your answer.
Set-up A: The bulb does not light when you disconnect the switch end from the dry cell.
This is so because the circuit is incomplete.
Set-up B: The bulb lights when you connect the switch to the dry cell. The set up is said to be a complete
15.6 dangers of electricity
Activity 15.9: investigating dangers of electricity
Charts and cut-outs showing dangers of electricity What to do:
(i) Obtain charts and cut-outs that show the dangers of electricity.
(ii) Observe the charts and pictures. Write down the dangers that you have observed in your notebooks.
(iii) Browse on your XO laptop about the dangers of electricity.
(iv) Read the following poem
Electricity is wonderful,
It makes our lives colouful,
But wait, it can also be shocking,
This poem can be the unlocking.
Electricity from the mains, so powerful,
It’s not like from the dry cells, so peaceful,
It can be colourful, yes but it can kill you !
Please listen carefully, yes it can kill you !
Stop! No metals in the plugs,
Watch out! That wire is exposed,
No! don’t touch with tiny wet hands!
Don’t take the risk, always ask for help.
(a) Come up with a suitable title for the poem.
(b) Outline 4 dangers of electricity mentioned in the poem.
(c) Who do you think the poem addresses? Justify your answer.
(d) Write down ways in which one can avoid dangers caused by electricity.
(v) Make a poster to warn or teach your friends about dangers of electricity.
(vi) Electricity was installed in Mr. Ivan house last weekend.
The electrician forgot to install a switch in his bedroom. What problems will Mr. Ivan have?
Electricity is a very useful form of energy. It is important for you to be careful when using it,
because it can be very dangerous.
When mishandled, electricity can cause dangers such as:
• Destruction of electrical appliances
The following practices should be avoided because they increase the dangers of electricity. • Inserting nails and other metallic objects into sockets.
• Touching electrical appliances with wet hands.
• Repairing electrical appliances while still plugged in. • Operating electrical appliances with damaged cables.
List 5 other practices that should be avoided.
Revision Activity 15
1. A bicycle dynamo produces electricity when the bicycle is at rest. TRUE/FALSE
2. Observe the following circuit diagram. Will the bulb light up? Explain.
3. Name any two sources of electricity that you use in your homes. 4. Explain briefly how a solar panel produces electricity.
5. (a) Construct a circuit with two dry cells and one bulb.
(b) Draw the circuit you have made
(c) Label all the parts of the circuit.
6. Name two materials that are good conductors of electricity. 7. Write down 3 ways of preventing the dangers of electricity when using electrical appliances.
Jeanette made the following circuit from locally available materials.
8. Name four materials that she used to make the circuit. 9. Jorum wants to improve on Jeanette's setup so as to make the bulb light more brightly.
What should he do?
10. (a) When Jeanette left the circuit on for a long time. The bulb stopped lighting.
What might have happened?
(b) How can Jeanette solve the problem in (a) above?
11. (a) Name any 3 electrical appliances that have the part shown below.
(b) What can happen if an electric appliance has the damage as shown in the picture? (c) What measures will you take if you have an electrical appliance that has the damage shown in the picture?
Word list 1.
Read the following words in pairs.
• Dry cell
• Electric shock
• Solar panel
• Electric metre
2. Spell 3 words while your friend writes them in his or her notebook.
Let your friend also spell 3 other words as you write them in your notebook.
3. Discuss with your friend the meaning of any 3 words in the word list. Refer to notes in your textbook.