Technicians - Electromagnetic Magic

Safety:  

Powerful magnets can affect electronic devices so care must be taken with phones, and electronic medical implants. - Control measure: warn audience 

If strong magnets collide, they can trap skin or shatter into sharp fragments – Control measure: use of jar lids to reduce the risk of collision. 

Wires can get hot with high currents – Control measure: use 1 volt and sufficiently long wires reduce the current. 

High currents can damage amplifier electronics – Control measure: use long & thin enough wire to reduce the current (100 turns plus one metre of 36 SWG (0.19mm dia) enameled copper wire for making speakers  

You should carry out your own risk assessments before attempting similar methods. 

Content: 

Electromagnetism is likened to witchcraft or magic. This workshop aims to explain much of the topic with demonstrations, practical and a group activity. 

Starting with discussion on safety (se above), using our ‘Hazboard’, The idea of ferromagnetism – iron objects becoming magnets when in magnetic fields is introduced and demonstrated. 

This is followed by demonstrations of magnetic fields being induced by current carrying conductors, which explains how electromagnets work. 

A practical session follows, looking at the force produced by current carrying conductors in a magnetic field. This leads into a group activity where a pair of speakers are constructed and stereo music played through them. 

The generator effect is then demonstrated with a magnet in a coil producing an electric current and the demonstration of speakers also acting as microphones. 

The final section of the workshop looks at a pair of connected coils, into the centre of each a magnet is suspended on a spring. When on magnet is set vertically oscillating, there is a generator effect in that coil driving a motor effect in the other coil, where the magnet there is driven to oscillate either in phase, or out of phase depending on the polarity of the connection. It is then demonstrated that, if close together, the wires can be removed and the oscillation will still be transmitted. Further demonstrations show driving one coil with a signal generator can prove the ‘wireless effect is possible, and even music played over an air gap is demonstrated. 

Notes:  

Accompanying experiment sheets (with photos of the equipment), and notes (suggesting possible alternative equipment) are available on the ASE conference ‘sched’ website. 

They have been written to aid technicians and teachers to set up and carry out the practical activities. They are not intended as student worksheets. They show the apparatus available at King’s Ely, so you may have to adapt them to suit your equipment. Many items have been made ‘in-house’.