1. Do Now (10/10/13): What do Watts measure?
Where do you see labels in Watts?

2. Electrical Power

3. Questions to ponder What is electrical power?
How do you calculate energy?
How do you calculate cost of electricity?

4. Calculating Cost of Power
Cost is calculated as the amount per Kilowatt hour
Common cost is usually about $0.08 -$0.11 per kilowatt hour.
Calculations are made by multiplying the cost by the usage in kilowatt hours.

5. What is electrical power?
Electric Power , P , is the rate at which electrical energy is converted into other forms of energy
Unit for power : Watt(W)
1 kW = 1000 W

6. How do you calculate energy?
Power
Energy
Time
Energy= Power x time

7. How do you calculate energy?
If it takes 300 W kettle 30 minutes to boil the water,
(a) what is the electrical energy used in kWh?

8. How do you calculate energy?
Calculate energy in kWh
To find energy in kWh, the power must be in kW and time must be in hr.
1 000 W = 1 kW!!!!
Energy (kWh) = Power(kW) x time(hr)
= 300/1000 x 30/60
= 0.15 kWh
It takes 300 W kettle 30 minutes to boil the water.

9. How do you calculate the cost of electricity?
Step 1 : Calculate the electrical energy in kWh
Step 2 : Find the cost of electricity.
Electrical energy is sold in kWh
For example , each unit costs 20 cents. This means each kWh costs 20 cents

10. How do you calculate the cost of electricity?
Calculate cost of electricity
Step 1 : Calculate energy in kWh.
Energy (kWh) = Power(kW) x time(hr)
= 300/1000 x 30/60
= 0.15 kWh
Step 2: Calculate cost
Total cost = Energy (kWh) x cost per unit
= 0.15 x 20
= 3 cents
It takes 300 W kettle 30 minutes to boil the water. Calculate the cost if each units costs 20 cents.