# Electrical Efficiency LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices.

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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 second e.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 (kW h): the SI unit for measuring electrical energy usage -1 kW h 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 kW h per year -new clothes dryer uses 300 kW h 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 E out % efficiency = _____ x 100% E in

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: E out = 35 J E in = 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: E out = 35 J E in = 100 J Unknown: % efficiency E out Select:% efficiency = _____ x 100% E in 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. E out Select:% efficiency = _____ x 100% E in 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:E out = 850 JE in = 1200 J Unknown: % efficiency Select: E out % efficiency = _____ x 100% E in 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¢/kW h. 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¢/kW h. 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¢/kW h. 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¢/kW h 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¢/kW h. 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¢/kW h. 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¢/kW h. 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¢/kW h 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¢/kW h 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¢/kW h Unknown: 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¢/kW h 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

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