Chapter 11 Lesson 7, "Measuring Electricity"

Materials:

• Worksheet, 11-07, "Measuring Electricity"

Objective:

• Students explain what electric power is.
• Students will explain how electric power is measured.
• Students will research the answers to questions on a worksheet.
• Students will answer 7 questions about Measuring Electricity with 80% accuracy.

Anticipatory Set:* Show the students a light bulb and ask how you would know how much electricity is used to light and produce heat in this bulb. Next show this light bulb and point out the label on the top. Point out that every light bulb is different. Does anyone know how many watts a bulb like this uses. (5-7 watts) When you buy a light bulb the packaging will tell you how much voltage and most of the time that will tell you how much light is produced. However, in the last 10 years a new light bulb has come out. Most of you have probably seen these before. This light bulb uses a lot less electricity and and produces a lot more light. The small one is known as a compact fluorescent. Here is a regular fluorescent bulb that is used throughout your school. The manufacture's name is also on the bulb. Here is the different variety of fluorescent bulbs you can buy.

Teacher Input:* Obviously, lights aren't the only thing that uses electricity in our lives. There are many other things that use electricity to make our lives easier. These things all have a label either on the cord or the devise. The label will give you the measure of how much electricity the device uses. If you have a cord with a big box on the end like this the devise will changed the electricity in you home from 120V of AC to a smaller voltage of DC.

Show the students a multi adaptor using the doc camera.

Does anyone have an idea about how the electric company knows how much electricity you use. You have all seen something like this outside your home or school. This one has a series of dials that you have to read. Each dial stands for a number in a place value.The numbers read like a clock. Others are easier to read like this one. The newest ones have a digital reading and actually transmit the number to the electric company at the beginning of each month so that someone doesn't have to come around and read the meter. The electric company or city then develops a bill based on how much electricity you use. In some locations the bill will have a lot of different information like this one.

Electrical fires are one of the biggest fire hazards in a house. On page 341 the page is dedicated to helping you make sure the electricity in you home is safe. Here you see an outlet that is overloaded. This creates a lot of resistance and heat. You should also check for electrical cords that have been damaged. If electricity can flow from one wire to another a lot of heat can be created. Light fixtures all have a label for the maximum size of the bulbs. In this fixture if the bulbs are too big, too much electricity will flow through the cords which could melt them. Newer cords have one hole slightly longer than the other. You can not alter these because it ensures that electrical power flows the right direction. Electrical heaters like this one are dangerous in a number of ways. There is open electricity flowing and the heat can cause nearby items to catch on fire. This cord has a third prong that should never be removed. The prong ensures that if there is a problem in the devise electricity will flow to the ground and not through the user. Halogen Lights are extremely hot. They usually cause fires by catching nearby things on fire. Here is one that has been talked about since I was a child but it still happens where someone will be an idiot like this an try to use electricity in the tub. Toasters have electricity flowing openly within them. If you stick a metal object in like this expect to get a severe shock. Wires in the villages carry a lot of electricity. If they ever break and fall to the ground that wire could kill you. Even when the wires are in the air they can cause a shock to a person on the ground with a kite like this or a metal ladder or anything else that is touched to the wire. Since almost all of you cut wood you should also be aware that cutting trees near a power line can also cause a big problem.

Guided Practice:* Students will work in pairs or groups to answer the review questions at the end on page 342.

Independent Practice:* Students will read section 11-07 then complete the worksheet, 11-07 "Measuring Electricity"

Check for Understanding:* Take the quiz, 11-07 "Measuring Electricity"

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).

Alaska Content Standards Addressed in this lesson:

• SCI A-1 Students will understand models describing the nature of molecules, atoms, and sub-atomic particles and the relation of the models to the structure and behavior of matter (Structure of Matter);
• SCI A-8 Students will understand the scientific principles and models that
  describe the nature of physical, chemical, and nuclear reactions;
  state that whenever energy is reduced in one place, it is increased somewhere else by the same amount; and
  state that whenever there is a transformation of energy, some energy is spent in ways that make it unavailable for use (Energy Transformations);
• SCI A-9 Students will understand the transfers and transformations of matter and energy that link living things and their physical
• SCI A-15 Students will use science to understand and describe the local environment (Local Knowledge); and: