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

Generating Station to Home

Brainstorm  How can we reduce the amount of electrical energy that we use?

Traditional “Electrical” Heat

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

A Typical “Wet Cell”

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