Does the bulb light up when there are no batteries in the torch?
No
Energy and electricity
- What do cells and batteries do?
- What is an electric circuit?
- Where does energy come from in a power station?
- How does electricity get from a power station to where it is needed?
- How can we use electricity safely?
Cells and batteries
Batteries come in all shapes and sizes. Batteries are needed for many different purposes. Most torches, radios, calculators, cell phones, some toys and even cars, pacemakers and hearing aids need batteries to work.
Batteries are useful because they store chemical energy. When the battery is connected in an electrical appliance and the appliance is switched on, the stored energy in the battery is transferred to the appliance in the form of electrical energy to make it work.
Investigating the source of electricity in a torch.
MATERIALS :
- aworking torch
- an old, broken torch
INSTRUCTIONS:
- Turn your torch on and off. Can you see the bulb light up?
- Turn your torch off. Open it up and take the batteries out.
- Now turn it back on.
QUESTIONS:
What does this tell you about the need for batteries to make your torch work?
You need batteries for the light bulb to light up. This is because the batteries are the source of electrical energy.
Do you remember learning about transfer of energy in Gr 4? When the torch lights up, what is the chemical energy in the battery transferred to?
Chemical energy in the batteries is transferred into electrical energy. Electrical energy is then converted into light energy in the bulb.
Bring an old torch to school that can be taken apart. Look carefully at all the parts that make up a torch and make a list of what you find. Each part of the torch is needed for the torch to work properly.
batteries, light globe, wires, switch, casing, glass or plastic front
An electric circuit is a system that consists of different parts. We call these parts the components of the circuit. For example, batteries, light bulbs and connecting wires are components that can make up a circuit. When these components are connected the right way, electricity will be transferred from one component to another. In this example, the electricity would be transferred from the batteries through the connecting wire to the bulb and back through the wire to the batteries to complete the circuit.
Making a simple circuit
MATERIALS:
- 2torch batteries
- 1 light bulb
- connecting wires
INSTRUCTIONS:
Part 1
- Set up the circuit as shown in the following diagram.
- Make sure all the wires are connected to form a closed loop.
QUESTIONS:
What do you observe?
The globe lights up.
What happens when you disconnect one end of one of the wires?
The light goes out.
The one end of the battery is labelled positive and the other end is negative. Draw a diagram of the battery and label the ends as positive or negative.
Part 2
Set up a new circuit with 2 batteries and 1 globe.
Explain how you connected the batteries so the globe still light up.
Batteries had to be connected end to end, with the positive side of one battery touching the negative side of the other battery.
Did the globe glow brighter or dimmer than in experiment 1, or did it glow the same?
brighter
Explain your answer to question 2.
Two batteries contain more stored energy than 1 battery, more stored energy changes to more light energy
Describe an electric circuit.
An electric circuit is a pathway that allows electricity to flow or a system that allows electrical energy to move.
If you have access to the internet, there is a wonderful site that allows you to build circuits and do experiments. Go to and see if you can build some circuits. Experiment to see how to make the globes burn brighter and dimmer.
Batteries are actually made up of smaller parts, known as cells, that store chemical energy. Two or more cells connected end to end are called a battery. We will mostly refer to them as batteries, but keep in mind that `cell' is the scientific term for what most people call a battery in everyday life. One cell stores a small amount of energy. If we need to store a lot of energy we use a battery.
A car needs a lot of energy to start its engine. One cell does not have enough stored energy. Therefore, a car battery has six cells that are connected end to end inside the battery case. In this case, there is six times more energy stored in the battery than in a single cell. This gives the car enough energy to start the engine.
Good question Jojo! Let's find out in the next section.
Mains electricity
A battery has stored energy which can provide electrical energy. However, our homes, schools, shops, and factories cannot run on batteries. We use electricity for many different things every day. The main source of electrical energy is from power stations. We call this 'mains electricity'.
Power stations need a source of energy
Power stations use different ways to generate electricity. A power station needs a source of energy. In South Africa, most of our power stations burn coal to use the energy stored in coal to generate electricity.
Coal is not the only source of energy for power stations, there are also other types of power stations. Find out what these are and write down what source of energy they each use.
Types of power stations include hydroelectric (water), geothermal (steam), and nuclear power stations (nuclear).
Electricity is transferred in a huge circuit to our homes
From a power station, electricity is transferred through transmission lines held up by pylons. The transmission lines are part of the circuit that connects the power stations to where we need to use the electricity.
Do you remember learning about the structures of pylons in Gr. 4 in Matter and Materials? Remember they are made from triangular shapes and struts to make them strong and stable!
The transmission lines carry large amounts of electricity to substations in cities and towns.
From a substation, electricity is carried in smaller amounts to an electricity box for our home. From the electricity box, electricity travels through wires to the plug points and light fittings in our homes.
The above diagram shows how electricity is transferred from the power station to your home. Continue the diagram (use the space below) to draw the path of electricity once it is in your home and goes through the wires, wall socket and plugs to get to an appliance, such as the TV.
This is to assess the learner's ability to draw a flow diagram and translate words into pictures and text.
Safety and electricity
We use electricity every day. Electricity can be dangerous, so it is important that we use it safely. Electricity can give you an electric shock. An electric shock can hurt you badly or even kill you.
Electricity can cause fires and injuries, even death. Here are some rules for using electricity safely:
- Do not put anything into an outlet except a plug.
- Do not pull on the cord to unplug an appliance, hold the plug and pull.
- Dry your hands before you plug in or unplug a cord.
- If a plug is broken or a cord is cut or worn, do not use it.
- Do not plug too many cords into one outlet.
- Keep appliances away from water. Do not use a hair dryer if there is water nearby.
- If there is an electrical storm (with lightning), turn off and disconnect electrical appliances, like the TV and computer.
- Never touch any power lines.
- Some power lines are buried underground. If you are digging and find a wire, do not touch it.
- Do not fly a kite or climb a tree near a power line.
10 Safety tips for electricity
INSTRUCTIONS:
- Look at the pictures.
- Each picture shows an INCORRECT use of electricity or electrical appliance.
- Study the pictures and write a "Safety tip" for the situation in each picture.
- The first example has been done for you.
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Picture |
Safety tip |
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Never use an appliance that has a broken cord or has some of the metal wire showing through the cord casing. |
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Answers:
- Never use an appliance that has a broken cord or has some of the metal wire showing through the cord casing.
- Do not play outside when there is thunder and lightning. If this powerful natural electricity strikes close to you, it will try to get to the ground through you!
- Never play near to or on electric fences or power lines. These have live electricity running through them so you can get a shock without even touching them!
- Never use electrical appliances outdoors in wet weather or if you are wet. Water conducts electricity well, so you WILL get a shock if you are touching an appliance and water drips into the socket, cord or motor. Wear closed shoes with rubber soles when using electrical appliances. Never use electrical appliances barefoot.
- Never use electrical appliances in the bathroom. Remember, electricity can flow through water.
- Electricity can flow from one person to the next. NEVER try to pull someone who is being shocked away from the appliance. you will get shocked too! Use a non plastic/non metal object to separate them from the electrical source.
- Never put lots of appliances into one socket. Too much electricity flowing to one plug is dangerous. One multi-plug adapter is safe, but do not put adapters into each other. Rather use 2 different plug points.
- Never stick a metal knife into a toaster while it is on. First turn the toaster off and unplug it and use a wooden or plastic knife. Beware, electricity can flow through metals.
- Energy can be stored in cells and batteries.
- The cells or batteries are a source of electrical energy for an electric circuit.
- An electric circuit is a system that transfers electrical energy to where it is needed.
- A power station needs a source of energy.
- Electricity from the power station is transferred in a circuit to our homes.
- Electricity can be dangerous and needs to be used safely.
Why do torches need cells (batteries) to operate?
Cells (battery) are a source of energy for the torch. Chemical energy is stored in the battery which is changed into electrical energy and then light energy as the light glows.
What is an electric circuit?
An electric circuit is a pathway that allows electricity to flow or a system that allows electrical energy to move.
How is a battery different to a cell?
a battery is two or more cells connected end to end
Draw a diagram of a simple circuit containing one cell and one bulb so that the globe will glow.
diagram as in workbook
How is it possible that electricity that is generated at a power station, reaches a TV in a home that is far away from the power station? Describe how the energy is transferred from a power station to your home.
Power station through transmission lines supported by pylons to substation. From substation through distribution lines to electricity box in your home. From electricity box through wires in our homes to plug points and lights and appliances.
When should you NOT handle electricity or electrical appliances?
When you are barefoot, have wet hands or in the bathroom.
Choose the correct answer: If someone is being shocked by an electricity source, I should:
- Try to pull them away from the source of the electricity.
- Throw water on them to cool down the shock.
- Turn off the power source as quickly as possible then attend to them.
- Attend to them then turn off the power source as quickly as possible once they are safe.
Answer: C
Give a reason for the following statement: 'Do not play under or near power lines or electric fences'.
If the electricity fields are live, I can get shocked even if just standing close to the electrical source.