Chapter 11 Lesson 6, Parallel Circuits

Materials:

• Worksheet, 11-06 "Parallel Circuits"

Objective:

• Students will describe a parallel circuit.
• Students will explain what happens to the brightness of bulbs in a parallel circuit when more bulbs are included.
• Students will explain what happens to voltage when two batteries with the same voltage are connected in parallel.

Anticipatory Set:* Show the students a map of Alaska and ask how you would get from Fairbanks to Anchorage. Next tell them that there has been a rock slide near Denali park blocking Highway 1. Now ask them again which way they would go.

Teacher Input:* Parallel circuits are like roads on a map. There is always more than one way for the electricity to travel to get from the negative side of a battery to the other.Show the students this picture and describe the different ways that electrons can travel. So if one of the lights in a parallel circuit goes out and will not conduct electricity any longer the other light will not go out. When we use a switch with a parallel circuit it can have different effects on the bulbs. In this situation if the switch is turn off which bulb will go out. The switch is in the series part of the circuit so both lights are affected by it. In this case the switches affect only one bulb because they are put in a place where they affect the electron movement through only one bulb. Here we see a wiring diagram for a home alarm system. Describe how they both work but using the two types of circuits.

Show the students this wiring diagram and ask which light or lights are on if the battery and lights are good. Next show several diagrams and ask if it is a parallel or series circuit. Circuit 1, Circuit 2, Circuit 3, Circuit 4, Circuit 5. Discuss the last one with the students and ask them which lights would go out if you turn of a variety of the switches.

Remind the students about what happens when you put batteries in a series. When we put batteries in parallel like this that multiplying of voltage does not happen. Are these batteries wired in series or parallel? How about these two batteries? Show this diagram and explain the differences between wiring batteries in series or parallel. Show this diagram of four batteries in a circuit and ask how many volts are being put through the wires?

Next, Use these four pictures to talk about different ways that parallel circuits are used and why. Picture 1, Picture 2, Picture 3, Picture 4. In a house there are many different types of circuits used many different ways. Electricians really need to understand the flow to keep from burning down a house. Here is a good example. Suppose you wanted to control a single light from two different switches at each end of a hall. This is called a 3way circuit. Here is how it works. Last year when I was putting my electricity in the house I built. I needed to control my ceiling lights from my stairs, the entry door, the kitchen, and the stairs from the basement. This was a complicated system and called for using a 4way parallel circuit. This is how it works.

Guided Practice:* Have the students work in small groups, pairs, or individually to answer the questions on page 337.

Independent Practice:* Students will read lesson 6 as they complete the worksheet, 06-11 "Parallel Circuits"

Check for Understanding:* Students will take a quiz 06-11 "Parallel Circuits"

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-2 Students will understand the physical, chemical, and nuclear changes and interactions that result in observable changes in the properties of matter (Changes and Interactions 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-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: