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Electrical Efficiency
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Electrical Power: the rate at which electrical energy is produced or used.
-measured in Watts (W)-one Watt is equal to one Joule of energy used per second
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Electrical Power: the rate at which electrical energy is produced or used.
-measured in Watts (W)-one Watt is equal to one joule of energy used per seconde.g. 100 W light bulb uses four times as much
energy per second as a 25 W bulb.
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
kilowatt-hour (kWh): the SI unit for measuring electrical energy usage
-1 kWh is the use of one killowatt of energy for one hour-3 600 000 times as much energy as 1 Joule
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Efficiency: comparison of the energy output of a device with the energy supplied
e.g. Clothes dryers-older clothes dryer uses 800 kWh per year-new clothes dryer uses 300 kWh per year-they both do the same job so the new dryer is more than twice as efficient
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Calculating efficiency of a Device:
percent efficiency = energy out x 100%energy in
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Calculating efficiency of a Device:
percent efficiency = energy out x 100%energy in
short form:
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Eout
% efficiency = _____ x 100% Ein
Electrical Efficiency
Example: A light bulb uses 100 J of energy and produces 35 J of light energy. Calculate the energy efficiency of the light bulb.
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Example: A light bulb uses 100 J of energy and produces 35 J of light energy. Calculate the energy efficiency of the light bulb.
Given: Eout = 35 JEin = 100 J
Unknown: % efficiency
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Example: A light bulb uses 100 J of energy and produces 35 J of light energy. Calculate the energy efficiency of the light bulb.
Given: Eout = 35 JEin = 100 J
Unknown: % efficiency Eout
Select: % efficiency = _____ x 100% Ein
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Example: A light bulb uses 100 J of energy and produces 35 J of light energy. Calculate the energy efficiency of the light bulb.
Eout
Select: % efficiency = _____ x 100% Ein
Solve: % efficiency = 35 J_ x 100% 100 J
=35%
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Try this: A toaster oven uses 1200 J of energy to produce 850 J of thermal energy. Calculate the efficiency of the toaster oven.
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Try this: A toaster oven uses 1200 J of energy to produce 850 J of thermal energy. Calculate the efficiency of the toaster oven.
Given: Eout = 850 J Ein = 1200 J
Unknown: % efficiency
Select: Eout
% efficiency = _____ x 100% Ein
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Try this: A toaster oven uses 1200 J of energy to produce 850 J of thermal energy. Calculate the efficiency of the toaster oven.
Solve: % efficiency = 850 J x 100% 1200 J
= 71%
therefor the toaster oven is 71% efficient
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Cost of Operating Electrical Devices:
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
cost to operate = power x time x cost of used electricity
Electrical Efficiency
Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.
Given: power = 75 W= 0.075 kW
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.
Given: power = 75 W= 0.075 kW
time = 24 hours per day for 365 days= 8760 hours
cost = 5.6¢/kWh
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.
Unknown: cost to operate
Select: cost to operate = power x time x cost of used electricity
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.
Unknown: cost to operate
Select: cost to operate = power x time x cost of used electricity Solve: cost to operate = 0.075 x 8760 x 5.6
= 3679¢ ($36.79)
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.
Unknown: cost to operate
Select: cost to operate = power x time x cost of used electricity Solve: cost to operate = 0.075 x 8760 x 5.6
= 3679¢ ($36.79)
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Try this: Calculate the cost of operating a 1500W hair dryer to dry your hair for 6 minutes per day for 3 days. The cost of electricity is 5.6¢/kWh
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Try this: Calculate the cost of operating a 1500W hair dryer to dry your hair for 6 minutes per day for 3 days. The cost of electricity is 5.6¢/kWh
Given: power = 1500 W= 1.500 kW
time = 6 minutes per day for 3 days= 6 min x 3= 18 min = 0.30 hours
cost = 5.6¢/kWhUnknown: cost to operate
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices
Electrical Efficiency
Try this: Calculate the cost of operating a 1500W hair dryer to dry your hair for 6 minutes per day for 3 days. The cost of electricity is 5.6¢/kWh
Select: cost to operate = power x time x cost of used electricity
Solve: cost to operate = 1.500 x 0.30 x 5.6= 2.52¢
LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices