Ralph G1BSZ of Verulam ARC: "What can we do to get youngsters involved with amateur radio?" After considerable thought I don't think we can on our own but the licensed grandads can. They could introduce their junior school age children to the wonder of ELECTRICKERY! A good place to start is the fresh potato/fruit cell. One electrode -VE (zinc) is a clean galvanised nail. The other is copper +VE. A bright clean copper penny will work but that's defacing coin of the realm so I use a copper nail. An analogue meter may not read so well as a digital meter. This may be due to the digital meter being powered by a PP3 battery that does not load the circuit nearly so much as an analogue meter. Alternative to fresh potato is vinegar or a fresh juicy lemon (yummy) as via link below. Insert the electrodes into the potato close but not touching i.e. one centimetre apart. Clip leads to connect electrodes to the multimeter. Usually it will read 1 Volt to 1∙5 Volts. Connect three in series to light an LED. Using a moving coil analogue meter the three cells together indicated 2 Volts. The DMM indicated 2.79 Volts. Varying the spacing of copper and galvanised nails on individual lemons produced little change in voltage readings nor did using small or large fruit. p.s. Citrus juice vapour is detrimental to delicate printed circuit boards. In 1800 Alessandro Volta invented the first battery. Two centuries later a project as above could fire a young child's imagination to greater things... Make/break the connection and you're into Morse code. CQ? Source: tinyurl.com/lemoncell My try at this experiment:
Cut the 3 lemons in half to create 6 cells. Wired in series = 5 Volts and the LED glows even brighter as shown above.

Another ELECTRICKERY! project for licensed grandad to show the children how the resistance of water and skin is affected by various factors. Take a beaker of distilled water (using preferably an analogue meter) display the resistance using e.g. thick bare copper wire as probes. An AVO meter with its large easy read display is ideal to show varying readings. AVOs start at £20 second hand off eBay. Then show how the resistance changes with bottled, tap & brine salt water. Let them use the meter probes to measure their skin resistance held loose and then tight and in different places both dry and with perspiration. WARNING do not encourage children to 'taste test' of e.g. PP3 or any batteries. We've all done it but IMHO that could damage the delicate nerves of the tongue.

Two more Ω demonstrations: 1) Light Dependant Resistor e.g. LDR 5528 or GL5528 with analogue meter & torch shows effect of dark & light. 2) Similary Thermistor e.g. NTC-MF52 103/3435 10k Ω to show Ω differences from e.g. ice water to hot water again with analogue meter. Heat shrink tubing for brief splash proof protection.

Connect a microphone to your meter. You may need a preamp but the onboard microphone of a lap top PC is ideal. Use the onboard microphone set to maximum gain, headphone out to analogue meter e.g. 0∙1 to 0∙01 AC Amps and then invite children: Let's have a competition. How loud can you children shout?... Is that all?!" Their efforts are displayed on the meter. "What musical instruments can you play?" WARNING: Unplugging lap top PC headphone jack with microphone at high sensitivity may cause loud high pitched oscillation feedback loop.

Static charges typically occur when we remove a sweater and it crackles. Build a gold leaf (I use aluminium) electroscope with an empty coffee jar. Stiff copper wire spiralled then straight through the plastic lid with hook to support bent over aluminium (leaves) in the jar. Take a piece of vinyl and rub it. That will induce a charge that is displayed by the leaves separating when brought close to the lid. Google: 'electroscope' or follow: tinyurl.com/ruelectroscope
73 Bob Houlston G4PVB MA3053SWL