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Electrical Safety in the home. GFCIs (Ground Fault Circuit Interrupters). Protects people from electrical shock by opening circuit when more current is flowing out of red terminal than into black terminal. Surge Protectors.
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GFCIs (Ground Fault Circuit Interrupters) • Protects people from electrical shock by opening circuit when more current is flowing out of red terminal than into black terminal
Surge Protectors • Protects devices from momentary surges of high current by diverting the extra electricity into the ground (through the third prong)
Fuses • Protect devices from electrical meltdown due to a current that is too high • Connected in series with the circuit’s load(s) • If current gets too high thin metal filament burns out, opening circuit and stopping flow
Circuit Breakers • Protect devices from electrical meltdown due to a current that is too high • If current gets too electromagnet pulls on metal switch to open circuit and stop flow
Brainstorm • How can we reduce the amount of electrical energy that we use?
Calculating Power • Power is measured in units of Watts (W) • Power = Voltage x Current • P = V x I • Ex. A small colour TV is connected to a 120V outlet and draws 1400 mA of current. Calculate its power rating:
Electrical Energy • Energy is measured in units of Watt-hours (W-h) • Energy = Power x Time • E = P x t • Ex. How much energy does a 60 W bulb use if it is left on for one whole day?
Cost of Electricity • The rates we pay for electrical energy are quoted in dollars per kiloWatt-hour • Your total cost for electricity is found by: • Cost = Rate x Energy • Ex. How much does it cost to operate a 0.12 kW fridge for one year if energy costs $0.08 per kWh?
History of Batteries • The first battery was created by Alessandro Volta • He used two different metals separated by a salt or acid to create a potential difference
What’s Happening • In the periodic table there are many different types of metals • Metals can either gain or lose electrons • What Happens? • A battery uses two different types of metals and the one metal steals the electrons from the other metal
Types of Batteries • There are two types of cells • Dry Cell – it doesn’t use a liquid to conduct the electrons but a paste • Wet Cell – uses a liquid to conduct the electrons • Other terminology • Primary Cells – non-rechargeable cells • Secondary Cells – rechargeable cells
Different Chemical Reactions • Different batteries use different metals to produce stronger or weaker potential differences (i.e. voltages) • Car batteries use lead oxide and lead • Alkaline Batteries use manganese dioxide, carbon and zinc