1. Power, Electrical Energy and Efficiency
Energy Costs
Calculations
Efficiency

2. KEY TERM - POWER Recall: Sports Venue example for Current and Voltage
Now that we’ve found the components which determine how much the venue will make, how do we calculate their total profit?
We need to take the number of people who came and multiply that number by the price per ticket.
This is the same for Electrical Power which is measured in Watts

3. Electrical Power Power (P)
The rate at which electrical energy is used = Current (the number of electrons passing by the point) X Voltage (how much energy they give up)
P = I X V
Measured in Watts (W)
1000 W = 1 kW
We mostly use kW

4. Typical Power Ratings of Appliances
Clock = kW
Clothes dryer = ________
Washing Machine = 0.5 kW
Computer with monitor and printer = ________
LCD TV = ________
Video game console = ________
Dishwasher = ________
Fridge / Freezer = ________
Home Air Conditioner = ________
Ceiling Fan = ________

5. Typical Power Ratings of Appliances
Clock = kW
Clothes dryer = 4.0 kW
Washing Machine = 0.5 kW
Computer with monitor and printer = 0.20 kW
LCD TV = 0.12 kW
Video game console = 0.10 kW
Dishwasher = 1.3 kW
Fridge / Freezer = 0.5 kW
Home Air Conditioner = 1.0 kW
Ceiling Fan = kW

6. Electrical Energy
The amount of electrical energy used is calculated by multiplying the number of kW X time (hours)
All household appliances must have an EnerGuide label which shows how much energy the appliance uses in one year and also gives the energy use per hour (kWh)
The higher the energy use, the more expensive it will be to run it!

7. Cost of Electrical Energy
The cost depends on the amount of energy used and the price that is charged for it.
To calculate cost you multiply the amount of energy used (kWh) by the price (¢/kWh).
E.g. Solve the following problem

8. Practice Re-Arranging a formula
P= I x V
But what if we need to solve for current or volts? We need to re-arrange the formula.
Let’s try it!

9. Working through word problems
GRASP method
Given (what do you know)
Required (what do you want to know)
Analysis (formula)
Solution (show your work)
Paraphrase (answer in a sentence)
ALL QUESTIONS WILL BE GRADED THIS WAY
Writing only the answer will get you 1/5