Contact in the classroom

7th March 2003 at 00:00
Science education suppliers offer a wealth of switches for classroom use, some more useful than others. I've a primary science catalogue in front of me, presenting 15 or more different switches on a single page. Some are simple onoff switches. Some look identical, but can be push-to-make (like computer keys) or push-to-break (like the fridge light switch). Some even toggle - the first push switches them on and the second switches them off.

Then there are the fancy ones. A "double pole" switch can be used to reverse the flow of current, and so change the direction of an electric motor. A micro-switch is just that - a tiny switch that costs pennies to buy but pounds for a washing-machine engineer to replace. Many of these have three terminals. One is "in" and the other two are "out"; using one or other terminal means that the same switch can be used to either make or break the circuit.

Reed switches are special switches that respond to a magnet. Putting one of these in a circuit and bringing a magnet close to them will switch the current on or off. They are useful in models - a magnet on a wheel will work the switch every time the vehicle passes a reed switch. Reed switches are contained in a tough glass tube and need handling with care.

Burglar alarm pads - operated by the weight of the boot of a careless burglar - are featured in the curriculum for science and design and technology. "Tilt" and "tremble" switches that respond to movement are used to detonate bombs. You can make your own - but be careful you're not arrested for running a terrorist training school.

Log-in as an existing print or digital subscriber

Forgotten your subscriber ID?


To access this content and the full TES archive, subscribe now.

View subscriber offers


Get TES online and delivered to your door – for less than the price of a coffee

Save 33% off the cover price with this great subscription offer. Every copy delivered to your door by first-class post, plus full access to TES online and the TES app for just £1.90 per week.
Subscribers also enjoy a range of fantastic offers and benefits worth over £270:

  • Discounts off TES Institute courses
  • Access over 200,000 articles in the TES online archive
  • Free Tastecard membership worth £79.99
  • Discounts with Zipcar,, Virgin Wines and other partners
Order your low-cost subscription today