Chapter 11 Lesson 4, "Ohm's Law"

Materials:

• Worksheet, 11-04 "Using Ohms Law"

Objective:

• Students will explain how current, voltage, and resistance are related.
• Students will use Ohm's law to calculate current.

Anticipatory Set:* Students will be shown four pictures of the label from electrical appliances. They will be asked what each label means. The letters may be unfamiliar to them so that will be covered later in the lesson. This should allow them to connect the formula to real world application. Label 1, Label 2, Label 3, Label 4.

Teacher Input:* The terms volts, Amps, and ohms can become very confusing when talking about all three at once. Use this picture to compare the three terms with water. This will help make the students more familiar with them. Voltage would be the height of the water column, Amps would be the amount of current, and a tap which allows water to flow is the amount of resistance or ohms. Next shows these in a simple closed circuit. Further describe the three terms along with common symbols used to represent them. First is amperes or amps. This is the current of the electrical circuit. The current tells how much electricity is flowing through the wires. The ohm is next. It is the obstacle to current flow and is measured in Ohms. Last is the Volts. What does this sign tell you? Remember that volts are the force of the push of electrons, like the height of the water tower. Recall from the study of atoms that scientists, mathematicians, and electricians do not like to right out everything so they use symbols for a lot of words and concepts. Here are some of those symbols when it comes to electricity. While teaching these things a man named Georg Ohm discovered that there was a relationship among volts, amps, and ohms. He found that the current in amps is equal to the volts divided by the resistance. Another common way to see is is volts equal the amps times the resistance. Just as 5 times 4 is 20, 20 divided by 5 is 4. It can be written several different ways using the mathematical communitive property. Soon it was discovered that a relationship between the power of the electricity can be related to the other three measures of electrical current. So in this diagram from Page 326. If the voltage is 1.5 and the resistance is .3 ohms, what is the amps or current flow. Many electrician and physicists that use electricity in there work have this chart nearby to use as a reference. It is an excellent way to keep Ohm's law straight in its many different forms.

Guided Practice:* Students will each be assigned one of these questions from page 324.

Independent Practice:* Students will read section 11-04 then complete the worksheet, 11-04 Ohm's Law.

Check for Understanding:* Students will take the quiz, 11-04 "Ohm's Law"

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-5 Students will understand the strength and effects of forces of nature, including gravity and electromagnetic radiation (Forces of Nature);
• SCI A-6 Students will understand that forces of nature cause different types of motion and describe the relationship between these forces and motion (Motion);
• 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-15 Students will use science to understand and describe the local environment (Local Knowledge); and: