Presentation on theme: "Measuring Electrical Energy Lesson 11. Measuring Electrical Energy What is Energy? Energy- The ability to do work Electrical Energy- The energy transferred."— Presentation transcript:
Observing sample circuits Circuit 1 has two 1.5 volt batteries in series producing a total of 3.0 volts. The circuit can keep the bulb lit for 5 hours.
Circuit two has two 1.5 volt batteries in series producing a total of 3.0 volts. There are two bulbs in parallel in this circuit which can stay lit for 2.5 hours.
Why does circuit two 2 last half of the time that circuit 1 does? It is using more energy.
Calculating Electrical Energy We can use a formula to calculate the amount of energy used in household appliances. Energy = Power x Time kWh kW h Total Energy Used = Speed That Electricity is used x How long electricity is used
How much energy is that? Examples : How many kilowatt hours of electrical energy are used by a kettle that has a power rating of 1.5kW and is operated for 1.0 hours? Energy = Power x Time E = P x T E = 1.5 kW x 1.0 hour E = 1.5 kWh
Using a vacuum cleaner runs 2 for hours with a power rating of 1.6 kW. E = P x t E = 1.6 kW x 2 h E = 3.2 kWh
Mowing a lawn for 3.5 hours with a mower that has a rating of 1.65 kW. E = P x t E = 1.65 kW x 3.5 h E = 5.78 kWh
Something to remember Power must be in kW 1000 W = 1 kW To change from W to kW divide by 1000
Example Example 1 400 W = ? kW 400 ÷ 1000 = 0.4 kW
Example Example 2 15 W = ? kW 15 ÷ 1000 = 0.015 kW
Example Example 3 3750 W = ? kW 3750 ÷ 1000 = 3.75 kW
Time must be in hours 60 minutes = 1 hour To change from min to hours divide by 60