Unit E: Electrical Applications
Chapter 11: Electrical Energy
11.5: Using Electrical Energy
pg. 434
Key Concepts:
1. Electrical energy production has an effect on the
environment and society.
2. Electrical energy should be conserved and used wisely.
Cooking, listening to music, using the computer, and light
bulb electricity. Devices that use batteries, such as; MP3
player, laptops, and cell phones, require electricity to
charge their batteries. Batteries store electrical energy until
you require it.
Batteries can supply our needs but they do run out of
energy very quickly, D, C, AA batteries. Large appliances
can not run off of batteries, they require large amounts of
energy to function, that batteries can not supply. It is
cheaper to get electricity from the grid them rely on
batteries at a cost of $100 per hour.
Using Energy Responsibly at Home
Electrical Energy Consumption: the amount of electrical
energy used, often measured in kilowatt hours.
Reducing unnecessary usage of electricity is responsible.
Electrical energy consumption is how much energy you use
measured in kilowatts. To determine this you need to
understand how different devices use energy.
Table 1: Energy Use and Costs of Household Appliances ($0.10/kX.h)
Device
Typical Consumption (W)
Cost per hour ($)
Heat pump or central air
15 000
1.50
Water heater or clothes
4 000
0.40
dryer
Hair dryer
1 200
0.12
Refrigerator
1 000
0.10
Computer and monitor
400
0.04
Light Bulb
60
0.01
Hidden Consumption
TV’s, computers, DVD players and many other devices
have a standby mode. Energy is continuously used as long
as hey are plugged into the wall outlet. This energy use is
known as the phantom load. Phantom loads account for as
mach as 7% of household energy usage.
Chargers are also energy consumers, they continue to use
energy even after the battery has been charged, and also if
they are plugged in, yet not attached to a device.
Using Energy Outside the Home
Electrical devices are used all over our community, in fire
departments, police stations, municipal offices, shopping
malls, schools, and hospitals all use phones, computers,
lights, machinery in factories.
How We Measure Electrical Energy Use
Energy is measured in kilowatts per hour (kW.h)
Each home has an electric meter which measure energy
usage in kilowatts per hour. An energy company uses the
measurements to bill the home owner for energy usage.
Efficiency
Efficiency: a measure of how much useful energy an
electrical device produces compared with the amount of
energy that was supplied to the device.
Not all electrical devices us electricity efficiently. Light
bulbs convert electrical energy into heat energy and light. A
100 W incandescent light bulb, uses four times more
energy then a 25 W compact fluorescent light (CFL), yet
they both give off the same amount of light. Light-emitting
Diodes (LEDs) use even less energy then the other two
types of lights.
Calculating the Cost of Electricity
To calculate the energy usage of a electrical device, you
need to know how much energy is used, and the price of
each unit of energy. Using the wattage of a device and how
long you use it is used to determine energy consumption of
the device. Watts can be converted into kilowatts.
To calculate cost of Electricity:
Energy used:
energy used (kW.h) = wattage (kW) X time (h)
Cost of Operating a device:
Cost to operate ($) = energy used (kW.h) X price of
electricity = ($/kW.h)
Sample Problem #1:
Check Your Learning:
Questions 1 – 5, pg. 438
Wrap Up:
- Electrical devices vary greatly in the amount of electrical
energy they consume.
- We can reduce energy consumption if we understand how
electrical devices use energy at home and outside the home.
- Electric meters keep track of how much electrical energy
is used in units of kilowatts hours.
- Some devices are more efficient at using electrical energy
than others.
Tech Connect: Storing Energy in Salt, pg. 439