Resources: Iron nail, insulated wires, battery cell, variable resistor, switch and paperclips.
Handout: Questions related to the Mission Assignment and space for students to draw their diagrams.
Use the previous lessons and unit to recap on the relationship between magnetism and electricity and how these two forces can work together.
Ask the students: why do you think it would be useful to be able to turn a magnet on and off? Do you think this is even possible?
Introduce the electromagnet, identify its components and compare it to a bar/permanent magnet. When the class is ready for the practical, they can watch the Mission Assignment video and then start on the investigation. The students will first build an electromagnet by wrapping insulated wire around an iron nail and connecting one end of the wire to a battery cell and the other end to a switch. Their electromagnet circuit should also include a variable resistor to change the current being supplied to the electromagnet. Only one variable must be changed at a time to keep the investigation fair. To stretch themselves, they could test the strength of the magnets using smaller pieces of metal (e.g. by cutting up the paperclips) to get a higher precision of results.
Career Film: Take a tour around Rolls Royce SMR's Heritage Museum in Derby to find out about Osman Bawa's job. Osman works as the Integrated Management Systems Manager for Rolls Royce SMR.
Expert Film: This is Graeme Sutcliffe. Graeme works as the Engineering Test Lead for Rolls Royce SMR. Listen to Graeme as he explains how to build an electromagnet.
Build an Electromagnet
The students will be investigating how the strength of an electromagnet can be varied. They need to consider how the number of turns in the wire and the amount of current passed through the wire affects the strength of the electromagnet.
To test this, they will see how many paper clips the iron nail can pick up after changing a variable.
Support Task: Have 4 or 5 different setups around the lab. Ask the students to make just one change at each station, for example:
Station 1 - increase the voltage from 2 to 4 volts.
Station 2 - increase the number of turns from 20 to 30 turns.
Station 3 - test the electromagnet with and without the core.
Challenge Task: Once the practical is complete, ask the students to design the strongest yet safest electromagnet they could make in the lab to pick up the most paper clips. The students could then demo their predictions one at a time in a class competition.
Once the practical is complete, the students can discuss their findings and predict the way to make the strongest yet safest electromagnet.
Electromagnets are magnets that require a flow of electricity to produce a magnetic field. Without a flow of electricity, there will be no magnetic field. Electromagnets usually have many coils of conductive wire wrapped around a piece of magnetic metal. When a flow of electricity travels through the wire, a magnetic field is produced. Therefore, the more coils of wire, the stronger the magnetic field will be.
Mission Assignment: Electromagnets can also be made stronger by altering the flow (the current) of the electricity, which can be done using a variable resistor or by changing the voltage applied to the electromagnet. If the resistance is lowered, the current will increase. If the voltage is increased, the current will also increase. This can be calculated using the equation: current (Amperes) = potential difference (volts) /resistance (ohms).