Approaches to learning about electricity and magnetism

Safety issues

Work on the topic of electricity and magnetism will provide opportunities for children to learn about the safe use of electricity. It is important that children realise the dangers of mains electricity and become aware of and discuss safety issues associated with the use of mains electricity and electrical appliances. Batteries should be used for activities based on electric current. Mains electricity should never be used during science investigations.

The children should be aware of the following safety, considerations:

• the dangers of touching the bare metal of a plug or a switch especially when hands are wet
• the importance of not using electrical appliances without adult supervision
• the dangers associated with flying kites or using fishing rods near overhead wires
• the risks attached to playing near electricity sub-stations.

Equipment

The types of batteries required for work on electricity are shown below. The battery voltage suggested in the exemplars that follow is by way of example only. Other batteries could be substituted. However, the battery voltage should be about the same as that specified on the bulb, for example:

Commercial bulbholders can be obtained through science suppliers. However, improvised bulbholders can be made by the children, using

• Plasticine
• clothes pegs
• plastic film cylinders. Punch a hole in each end of a round film holder (the cylinder used to contain 35 mm film). Insert a brass paper fastener and press it open. Attach the wires to the brass paper fastener. An R6 battery should fit exactly inside the holder. The circuit is made as the terminals of the battery touch the brass paper fasteners.

Activities on electromagnetism may require the use of nails. Teachers should ensure that only blunt nails are used; hammering the tip of a nail will achieve a blunt finish.

Crocodile clips can be used to make connections in circuits. These are particularly helpful for younger children, who may not have the manual dexterity to use a screwdriver to connect leads. It may be necessary to mount bulbholders onto wooden blocks and connect the crocodile clips to screw eyes.

Safety and care of equipment

Work on electricity at all levels will involve the use of batteries. The following safety procedures should be observed

• batteries must not be cut open
• batteries should be disposed of in a safe manner. There may be a battery recycling depot in the locality
• rechargeable batteries should not be used for investigations
• leads, composed of lengths of insulated wire, will be necessary for making circuits. The teacher or a specially designated adult can strip the plastic covering from the leads using wire cutters and strippers or a sharp scissors. Children should never undertake this task.

Electricity

Static electricity

Static electricity occurs when an electric charge builds up on an object. This build-up can happen by rubbing one material against another. Electrons are rubbed off one of the materials, which then becomes positively charged, while the other material, which gains the electrons, becomes negatively charged. The two materials then attract each other, for example rubbing a balloon against a woollen jumper.

When a charged object is connected to another object or to the Earth, electrons flow between the objects. This can be experienced as a slight shock by a person when a car door is touched after moving against upholstered seats or as the crackling sound of hair when it is combed after being washed and dried. Exemplar 25 illustrates how a lesson on static electricity may be structured for first and second classes.

Electrical energy

Starting from children's ideas

It is important to recognise that children are likely to have prior ideas about electricity, which can be explored and challenged by posing questions such as:

What sort of things use electricity?

Children make two lists or two collections of things that run on mains electricity and those that are batterypowered. Some objects, such as radios, computers and hand drills, may come under both headings.

How does electricity get to where it is needed?

Children can draw pictures showing the electrical supply to their house or school. Older children can make annotated drawings of how electricity gets to a bulb from a battery or from the mains supply to an electrical appliance.

It is likely that children will not be aware that a full circuit is needed for electricity to flow. Their own experience will suggest that only one wire or cable is required: for example, the children will observe that only one wire is leading to every electrical device in the house. It will be important that children have plenty of opportunities to establish the idea of a full circuit.

EXEMPLAR 25 - Static electricity (first and second classes)

Current electricity

In the middle and senior classes children should have opportunities to construct circuits with batteries, wires, and components such as bulbs, switches and motors. They will discover how to make bulbs light and make switches and motors work. Investigations with electricity will provide many opportunities for activities with a technological focus. Children will design and make a variety of their own switches, using different materials and for different purposes.

Exemplar 26 describes how children in third and fourth classes can make a simple circuit. This activity is also suitable for older children who are starting work on this topic.

Making circuits with two or more bulbs

Children in the senior classes will be guided to investigate how to make circuits using series and parallel wiring. In a series circuit the electricity flows through each bulb or component. When one bulb is removed the circuit is broken and all the lights go out. Children may discover that the more bulbs that are added to the series circuit the dimmer the light from each bulb becomes.

In a parallel circuit each bulb has its own circuit to the battery. If one of the bulbs in a parallel circuit is removed, no other light or component will be affected. When bulbs are in a parallel circuit each of the bulbs receives the same flow of electricity from the battery. Therefore the bulbs are equally bright.

When children have succeeded in lighting bulbs in series and parallel circuits they should be prompted to investigate the following questions:

Which circuit produces the brightest lights?
What happens if one bulb is removed from each circuit?
How long does a battery last in a series circuit and in a parallel circuit?

Conductors, insulators and switches

Conductors are materials that allow electric current to pass through them. Metals are the best conductors of electricity and are used for electric wires. Rubber, plastic, glass, cloth and other non-metallic materials are poor conductors. This explains why appliance plugs and electric wires are covered with rubber or plastic. Exemplar 27 is an example of an investigation based on conductors and insulators.

Children should investigate materials that allow electricity to pass through them. They should make simple on-off switches. Older children can make twoway switches.

Electromagnetism

In the senior classes children will explore how electricity and magnetism work together. They will discover that when a current passes through a coil of wire, the coil acts like a magnet. Exemplar 28 illustrates how a lesson on electromagnetism may be structured and how children can investigate the factors that affect the strength of an electromagnet.

EXEMPLAR 26 - Making a circuit (third and fourth classes)

EXEMPLAR 27 - Conductors and insulators (third to sixth classes)

EXEMPLAR 28 - Electromagnetism (fifth and sixth classes)

Magnetism

Children will discover that magnets exert a force that can cause some things to move. We call this pull magnetism. In the infant and junior classes children will notice that some objects move towards the magnet before it touches them. They will also discover that some materials are not attracted to magnets. In the junior classes children will sort materials into sets: a set of magnetic objects and a set of non-magnetic objects. Children will discover that the magnet attracts only metallic objects.

However, they will notice that not all metallic objects are magnetic. Children should observe that the pull of a magnet can pass through certain materials, such as water, glass, plastic and paper. In a magnet the force of attraction is concentrated at two points, known as the poles. Children can experiment to discover that magnets attract and repel other magnets. Similar or 'like' poles repel each other, and different or 'unlike' poles attract each other. The north-seeking pole of a magnet is referred to as the north pole, and the south-seeking pole is referred to as the south pole. Children will discover that they can make a magnet by stroking a steel sewing needle with the pole of a magnet. When a magnet can move freely (sewing needle placed on a cork in a basin of water) it will come to rest with its north pole pointing towards magnetic north.

Children can observe the pattern of a magnetic field of one or two magnets by using iron filings. Place the filings in a transparent plastic box and place the magnet on the box.

Exemplar 29 illustrates how this topic may be developed in the junior classes.

Safety and care of equipment

Magnets need to be stored carefully to preserve their magnetism. They should be stored with their keepers. The keeper is the small metal bar that should be placed across the poles of a magnet. If magnets are stored in pairs, unlike poles should be put together in the box. Heating, hammering or repeatedly dropping magnets will cause them to lose their magnetic properties.

EXEMPLAR 29 - Magnetism (first and second classes)