Science -- Your Future, Scotland's Future
SCI-FUN Roadshow Exhibits -- Human Circuit
SCI-FUN Roadshow Exhibits -- Human Circuit
In this exhibit you learn about how different amounts of electricity can affect us.

When you made a human circuit, small amounts of electricity flowed across your skin's surface. This activited an electronic switch, allowing a much larger amount of electricity to flow through the lamp and light it up.

You couldn't feel the 0.01mA that flowed through you (or even you and your friends), but the 700mA that went through the lamp would probably kill you. Currents even higher than this run through many of the electrical appliances you use every day: this is why electrical safety is so important.

Severe electric shocks cause your muscles to contract sharply. With even greater current you may stop breathing, have a heart attack, or your heart may stop completely.

The minor electric shocks we receive, often when touching a car door or a metal handrail, are due to static electricity. As you move around, parts of your body rub against other things, like your feet against the floor or your body against a chair. This causes a charge to be built up. When you touch something metal, which conducts electricity, the electricity moves into the metal object, giving you a shock. Sometimes you might even see a spark. These shocks are not dangerous.

Dangerous electric shocks occur when you are connected to an active electrical circuit with a high current. If you were so foolish as to poke metal into the bottom two holes of a plug socket, that would connect you up to 230V of mains electricity, which could easily kill you. Similarly if you open up an electrical appliance (perhaps to fix it) while it's still plugged in and touch two parts of the circuit, you'll also be exposed to high voltage (probably not as high as direct mains voltage but still enough to to do you some serious damage, if not kill you). This is why you must always unplug an appliance before attempting repairs on it. You can also get electric shocks by touching two ends of a battery with wet hands: this is painful but essentially harmless.

Power lines and railway tracks are also sources of dangerous high voltage, and should be avoided.

1 In the Human Circuit small amounts electricity flowed across your _______'s surface.
2 How did the larger current, going through the lamp, get switched on?
3 What happens to your muscles when you have an electric shock?
4 What are minor electric shocks, like we might get from a supermarket trolley, caused by?
5 What must you do before attempting to repair an electrical appliance?
6 Do you know of a natural phenomenon caused by static electricity? You might have encountered it in another SCI-FUN exhibit.

1 Different shoes will affect your chances of getting static electric shocks. Put on different shoes then walk around, scuffing them against the floor. Then touch something metal, like a door handle, to get an electric shock. Take note of how powerful the shock was, and what the soles of your shoes were like (what they're made of and how thick they are). Do you notice any patterns?
2 Scalextric and toy train sets both work by having two metal tracks which are connected up to an electrical source. When the car or train is placed on the track, a connection is made and this completes the circuit, powering the motor in the vehicle. Do you feel an electrical shock if you touch the two rails of a Scalextric or train track with the power on? Can you power anything else by touching it to the tracks? Based on your observations, do you think it is a strong current in the rails? Why is it important for the manufacturers to make it like that?