Magnetism and Electromagnetism
The basic ideas of magnetism, interaction between magnets and magnetic objects and magnetic fields should have been covered at primary level and again at KS3 and so it would be hoped that students will be familiar with them although it is worth checking. The idea of a ‘field’ around a magnet can be conceptually demanding for some, they may have seen the field lines in a diagram or demonstration but these are imaginary constructs and not a ‘real’ thing in the way that the magnet itself is considered real.
It’s common for some students to struggle when learning about transformers, motors and electromagnetic induction. It requires the combination of an understanding of the relationships between current, potential difference (and resistance) as well as the interaction between magnetic fields and charge carrying conductors. It is also common for the magnetic effect of a current, the electric motor and the generator (dynamo) to be taught a separate phenomena rather than all part of the same set of ideas. Individually they may be easy to demonstrate (current carrying wire moving in a magnetic field, moving wire in a magnetic field induces a current) but connecting all of these together can be a challenge for students.
The multi-step process that takes the ideas from a generator (a changing magnetic field can induce a voltage in a conductor) and then applies this to the workings of a transformer can also be very challenging for some.
The building of electric motors can be a fun and engaging activity but equally the physical complexity of the activity can create barriers to understanding. The simple electric motor shown in the list below (electric motor) can help to show the interaction between a current carrying ‘wire’ and a magnetic field as a principle although can become quite complex if you look too closely at the magnetic fields involved.
As a final thought this video of Richard Feynman is an absolute classic in terms of physics teaching and well worth a watch.
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.
The PhET simulation Faraday’s Electromagnetic Lab *suitable for home teaching*
An interactive simulation that helps the user visualise how a changing magnetic field is able to induce an EMF.
Electric Motor
This little practical for students is ace, they will love it! Using just a battery, a magnet and a coil of wire, students make their own electric motor. Just make sure you use the new neodymium magnets, as older, traditional magnets simply aren’t strong enough.
You could use it in lots of different ways and here are two suggestions. Use it as a hook to engage students with the topic by getting them to make the motor before attempting any explanation. Alternatively, students could build the motor after having completed some theoretical work. Challenge them to present to each other or a small group, how this motor works.
Introducing Magnetic Fields and the Electric Motor Effect
Here’s a rather different approach to introducing electric motors. Rather than explain or give instructions about how to build a motor, students are encouraged to investigate and share their ideas with each other in small groups, before feeding back to the rest of the class at the end of the lesson. It’s a nice approach if you have the time since students are likely to be intrigued and want to know more. Make sure that you provide the new, strong neodymium type magnets. The resources consist of a lesson plan and teacher notes. The equipment they are provided with allows them to build a motor along the lines of the motor in activity in the activity at the top of this page so choose for yourself how to use this practical work best.
Electromagnetic Induction *suitable for home teaching*
In this video electromagnetic induction is explained using a well-designed and well-made generator. Show the video to your students and discuss with them how the device works.
Motors and Electromagnetism
This comprehensive booklet contains ideas and suggestions for practical activities that you can use to plan your lessons. It covers loudspeakers, simple motors and dynamos. If you have a class set of model motors you must use them. Your students will enjoy making one and they will be very pleased when it spins. For a wow demonstration try the falling magnet (resource sheet CR7) that requires a small supermagnet.
Bright Sparks: Practicals
From these six practicals there are three that are of interest here. The Shaking electricity is a make activity that uses a supermagnet in the construction of a simple generator. The Make a motor exercise uses another design for a d.c. motor that does not have a commutator and once finished works well. The Magnetism and electricity investigations make use of supermagnets to demonstrate magnetic force on a current carrying conductor and ferrofluid to see the field of an electromagnet.
Make your own electromagnet
In this activity, students make a nail into an electromagnet. They then investigate whether increasing the number of coils of wire, or the thickness or length of the nail, affects the strength of the electromagnet.
Electromagnet investigation and results
This video demonstrates an experiment to investigate how current affects the strength of a magnetic field. The Phyphox app on a mobile phone is used to measure the magnetic field strength. The second part explains how to plot a graph to evaluate the relationship between current and magnetic field strength.
Field around a magnet
This video introduces permanent magnets, their fields and how to investigate them using iron filings. It also demonstrates the field between attracting and repelling magnets.
Transformer output
The properties of a transformer are investigated in this video, specifically how the number of turns on the coils affects the output.