Students do not really understand how
important electricity is to our everyday existence. Public supplies of
electricity were not available to countries until the late 1800's.
England and the United States were leaders in the development of a
public system of power generation. Urban areas were usually serviced
before the rural areas. In the period between 1920-1950, the demand for
electricity made the "power company" an important part of our
everyday lives. Point out that there are different "types" of
electric current in different countries. You can't plug a hair dryer
bought in the United States into a European plug.
In the generation of electric power
from water, fuel, or nuclear, the heat energy is converted into
mechanical energy by a prime mover and then into electrical energy by a
generator. A generator is based on the "dynamo" principle - a
fast-moving substance which can generate electricity. This is much more
complicated but it is not necessary to go further than this in the third
- Many students may ask how
electricity is moved. Point out any transmission or power lines. In
California for example, much of the electricity is generated by
hydroelectric power. If a power plant is close to your school, try to
arrange a tour. Invite the janitor, or any member of the maintenance
crew from the school district, to give a lecture to explain the power
source at your school.
- People must pay for the luxury of
electricity. Private electric utilities are regulated by state or city
governments. The various laws require that power companies be permitted
to earn a reasonable profit. But how do we pay for energy?
- A school's electric bills are
based on two factors: the amount of electricity used, measured in
kilowatt hours, and how much is used at any one time (or kilowatt
demand). Schools have two meters; one meter to record the total kilowatt
hours used; the other to record the largest number of kilowatts used at
any one time.
- If students want to lower the
school's energy expenses, they will need to do more than use less
electricity. They will also need to keep from using a large amount of
electricity at any one time. Example: If the cafeteria is preparing
lunch from 9 a.m. to 12 p.m., students should ask the shop teacher not
to operate the machines LAB this time. This will keep the school's
electrical demand lower.
- Some of the portions of the lab
sheet were designed by Pacific Gas and Electric Company. They will help
your students see how electricity is recorded. Many places are a little
more modern, but many old buildings still use a meter.
- To make a meter card you will
need: brads, stiff paper (about 60 lb paper), pen, circle template
A meter card helps gas companies read
meters that may not be assessable to meter readers. Make 5 circles and
number the circles as below. Put the brads in the center. Make a
"hand" that students can rotate to any of the numbers on the
rim. Students will use the hand to help read the meter.