Electrical Safety

1. Electrical Safety • & Cells and Batteries

2. Fulgurites • Lightning can be dangerous because it discharges so much energy. • Lightning strikes can actually melt sand and rock when they hit the ground.

3. When lightning melts sand & rock… • It creates glass-lined tubes called fulgurites.

4. Electrical Safety • January 1998 eastern Ontario and Quebec were hit by a massive ice storm. • Any person coming into contact with a power line may create a path for electricity. • This path is sometimes called short circuit.

5. Without a complete circuit… • Electricity cannot flow. • If electricity can find another path, such as through a person’s body to the ground, then it will take that path. • Ice Storm

6. Dangers of Electrical Shock • Two important aspects of electricity: voltage & amperage. • High voltage is more dangerous than low voltage; 50 000 V more likely to kill you than 10 V. • Even small voltages can kill if the shock carries a significant number of amps (rate of flow).

7. Amps more important than voltage: • When assessing the potential danger of electrical shock. • 0.001 A passing through your body- likely would not feel it. • 0.015 to 0.020 A- painful shock & loss of muscle control. • Current as low as 0.1 A can be fatal.

8. Factors affecting electric shock:

9. Current does not flow easily: • Through insulators such as wood, rubber & air. • You might feel just a tingle if you touch an electrified fence on a dry day when you are wearing running shoes. • But, you could get a nasty shock if you touch the fence when you are barefoot in the rain.

10. Every plug-in device: • Sold in Canada must have a label listing what voltage it requires and the maximum current it uses.

11. The amperage rating does not have to be high for you to get a shock. • If there is a short circuit or if the insulation is damaged, you could get a shock from the electricity before it goes through the device.

13. Plugs, Fuses & Breakers • Grounded 3 prong plugs have an extra wire that connects the device to the ground wire of the building. • It provides another pathway for electricity, just in case there is a short circuit. • Electricity travels to the ground instead of through the user.

14. Fuses • Interrupt a circuit when too much current is flowing through it. • Contain a thin piece of metal that is specially designed to melt if too much current passes through it.

15. Circuit Breakers • Have a special wire that heats up if there is too much current. • Hot wire triggers a spring mechanism that turns off the switch inside the circuit breaker. • As soon as problem is fixed/wire has cooled, the circuit breaker can be turned back on.

16. The danger of lightning • The current in a lightning strike can be as high as 30 000 A, and they can kill. • People can survive lightning strikes when the full amount of current travels over only part or over the surface of their bodies.

17. The danger of lightning • Lightening is a huge amount of negative charge and tends to seek the highest point on the horizon to discharge. • Tall buildings are a natural target for lightening strikes, and so often add lightening rods to their peaks- lightening rods are connected to the ground with a wire; discharge is conducted harmlessly to the ground.

19. Check & Reflect • Page 287, #s 1-9