Welcome to the sixth instalment of the ‘Making it Relevant’ series.
Firstly, we are going to take a look at why we teach Magnetism at GCSE. Then the content typically required in the new GCSE specifications will be summarised. Finally we will be thinking about how this can be made engaging and relevant to all our students. Planning a new scheme of work should involve looking at the big ideas you want to present, and then how to tailor them to your particular students.
Without magnetism we would have no electricity. The most experience some of your students may have had with this topic is writing rude words with fridge magnets. Very few will have used a physical compass (they have an App for that these days). Fewer still will have played with electric motors, even though they use them daily. This whole topic should instil a sense of how reliant we are on magnetism for everything from headphones to hair-dryers.
The main areas covered in this topic are:
The difference between permanent and induced magnets. Locating and representing magnetic fields. Why a compass works.
The Motor Effect
Turning a piece of wire into a useful electromagnet. Using Fleming’s Left Hand Rule to see which way conductors will move in a magnetic field. Applying the motor effect principle to headphones, loudspeakers and motors.
The Generator Effect
The factors influencing the size and direction of the induced current. Using the generator effect in dynamos, alternators and microphones.
Understanding the operation of transformers. Explaining how transformers make the National Grid more efficient.
Magnets are fun.
But there is a whole side to magnetism that your students have probably never considered, so a first step might be engaging them with this hidden side through the use of images and examples. With our ‘engaging girls’ hat on, please be careful here – there are many heavy engineering examples of electromagnetism. Your typical Y10 girl will not be enthused by a power station generator or a scrap yard magnet.
The concept of the motor effect will be most effectively demonstrated practically – seeing is believing.
The best lesson to watch the students get to grips with is definitely Fleming’s Left Hand Rule; you would be amazed how many can’t tell left from right! The contortions they get themselves into – it is almost worth recording for leavers assembly…
Before looking in detail at the operation of electric motors, for a homework you could try asking your class to write a list of all the things they use in a day which have electric motors in them. There’s the power shower, the electric juicer, the microwave turntable, the hair-dryer, the rumble-pack in the X-box controller and that’s just before school.
Most prep-rooms have electric motor kits, they are incredibly fiddly but always fun to build. I am not convinced that they are very instructive though, so for explaining the concept a good animation might be more appropriate. There are many on the internet, so pick one at the right level for your class.
The Institute of Physics have instructions for making a speaker here, which is a nice way to demonstrate a practical use of the motor effect.
The Generator effect and the idea of induced current will also be a new concept for your students to take on board. You can, again, show physically that current is induced with a simple coil, magnet and galvanometer. Be careful to distinguish between the potential difference always being induced, and the current only flowing if there is a complete circuit.
Transformers are fun to build – they are not terribly efficient though, so don’t plan on using them to verify the transformer equation. The Equation is something that those who struggle with maths will need more support with. You could try Transformer Top Trumps as a fun way to get loads of practise in.
Have fun with this attractive topic, you will be motoring through it in no time and generating lots of interest.