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Electrical safety
What can happen if you put something made out of metal into a toaster?
Oh yes! Nothing beats toast in the morning! Uhm, it looks like the toast is... toast. I'll get it out!
STOP! That's totally dangerous! NEVER put something made of metal into a toaster. You can get an electric shock! Did you know it's actually more frequent that people die from toasters than shark attacks?
Yeah, especially in the kitchen, huh! -- Perhaps that sounded like a joke, but every year many people get hurt, or even die, from accidents involving electricity. Therefore it's important to have some basic knowledge about electricity, and how it works. And how we protect ourselves. Oh, right now quite a few machines are operating at the same time. What happens if you use that much electricity at once?
Yes, look! A circuit breaker tripped. In all buildings, there is a junction box with a number of circuit breakers. When too large a current passes through a circuit breaker, it breaks the current. Every circuit breaker is related to a certain part of the building.
If there is too powerful a current through the wires... ... they can become too hot... ... and catch fire. A circuit breaker is a sort of emergency brake that switches off the current if it becomes too high. Many houses and apartments have older types of circuit breakers called fuses, that you have to replace when they have 'blown' and switched the current off.
On each fuse, you can read what current it is suited for: for instance ten amps, or sixteen amps. You have to make sure you replace it with the correct fuse. Modern buildings have trip-switch circuit breakers. All you need to do is reset the knob, button, or lever to switch on the current again. Philip, turn off the microwave!
Okay. And the stove! Okay. And the TV. Okay.
When Philip has turned off the machines in the kitchen, the current can flow normally again. Just to be sure, I'll turn off the coffee machine as well. No, Philip. Pull the plug, not the wire. If you unplug by holding the wire, the insulation inside the wire might break and cause a short circuit.
Then the current increases. The conductor gets hot; and the insulation might melt from the heat, exposing the wires. An exposed wire, if connected to a power source, is dangerous: you could get an electric shock. Never touch a live, exposed wire, and always disconnect before repairing it. -- Since we mentioned plugs: Have you noticed there are different types? And different types of socket?
What's the difference? If we look inside this plug we find two wires that carry the current to - and from - the appliance. Here, however, there is a third wire. If everything works like it should, no current flows through it. But, if something goes wrong - if something wears out inside this old toaster - the whole thing might become 'live'.
If you touched it, electricity could pass through your hand or body. The third wire, yellow and green, protects against just that. It carries the current away from the toaster down to earth, where it's harmless. We say that the plug is earthed or grounded. For this to work, both the plug and the socket need to be earthed.
There is often a complement to the earth wire, called an Earth Leakage Circuit Breaker, or ELCB. Within 3 hundredths of a second of detecting a current leakage in the earth wire, it shuts off the current in the supply wire. With earthed plugs and an ELCB in the building, you are well protected against electrical accidents. Oh, now this slice also got stuck. But, Philip...
Oh. Yeah! Safety!