Chapter 11 Lesson 3, "Some Sources of Electric Current"
Materials:
Objective:
Anticipatory Set:* Start with a review of Lessons 1 and 2 using this. Remind students at all electric power comes form the atom and that things with similar charges attract and like charges repel. Also items with a neutral charge will attract both positively and negatively charged objects as in this picture. These charges come for the protons and the electrons in an object. We can move the concentration of those particles around if the material is a conductor and allows us to do that. A conductor is something like this can that allows electrons to move freely from atom to atom. An insulator such as the cup does not allow electrons to move from atom to atom very freely. Everything is found somewhere on the line of being a conductor or an insulator. Using a charged object we can move electron around in a conductor. After we move those electrons around it is possible to remove electrons or protons and give that new item an electrical charge.
Show this animation of how to Induce a charge.
You can also use the ground to remove electrons. In this case the electrons move from the metal sphere, through the person's body and into the ground. When we started the chapter a couple weeks ago we looked at these characteristics with balloons. We talked about there needing to be a force but never defined what that force is. Does anyone know what we call the force that pushes these balloons apart or keeps the current flowing in an electric circuit?
Teacher Input:* There are some characteristics that we need to know in order to understand Electromotive force. Then this force can be harnessed and stored. Here is a simple way. Like water we can have a lot of force stored like the force stored behind the Hoover Dam. Or we can have a smaller force stored like the water behind this little dam. We store the electricity in a battery. Once the electricity is released the electromotive force can be measured. The metric unit of Electromotive Force is the volt. We can increase the force by using more than one battery. When they are connected end to end the force is multiplied by the number of batteries used. We measure this Electromotive force for many different sources of electric power. There are a couple different types of batteries. The most common type you will use is the dry cell battery. Here is how it is set up. Here is a wet cell battery. Explain it using this animation.
Batteries give an electromotive force that flows in one direction. Use this animation. However there is a type of electricity that flows in both directions. Here is a diagram from the site below. Diagram 1.
To explain the difference between alternating and direct current use this link. http://www.pbs.org/wgbh/amex/edison/sfeature/acdc.html
Alternating current comes from a generator. Here is what it looks like on the inside. The spin is usually powered in your villages by a big engine like this.
At the end of the section is an article you really should read. These three guys invented a transistor. There names are not very well recognized but with out there inventions we would not have radios, computers, or millions of other electrical appliances. Here is the very primitive transistor they created. We would still be using electricity only for heat and light. Here is how a transistor works. Does anyone remember the name for this type of diagram?
Guided Practice:* Students will work through the questions on Page 324 individually, in small groups, or as a class.
Independent Practice:* After reading Lesson 3 in the book, students will complete the worksheet, "Some Sources of Electric Current"
Check for Understanding:* Students will complete the on-line quiz, 11-03 "Some Sources of Electric Current"
Duration:
30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).
Alaska Content Standards Addressed in this lesson:
