Power, Electrical Energy and Efficiency Energy Costs Calculations 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 X V 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