Transcript The rate at which electrical energy is used

Power, Electrical Energy and
Efficiency
1. Power
2. Electrical Energy
3. Energy Costs
4. Calculations
5. Efficiency
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
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 XV
Measured in Watts (W)
 1000 W = 1 kW
 We mostly use kW
Typical Power Ratings of Appliances
 Clock = 0.0050 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 = ________
Typical Power Ratings of Appliances
 Clock = 0.0050 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 = 0.025 kW
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!
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
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!
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