1. Unit: Energy and Control- Electricity

2.  Think about a busy intersection. How do traffic signals control all that traffic? Advanced greens; green arrows; and green, red, and amber lights turn on and off. Each set of traffic signals include a complex arrangements of switched which control the lights. Traffic lights were invented by the African-American inventor Garrett A. Morgan. He developed his idea after witnessing an accident at a busy intersection. In 1913 he received a patent for his invention which is now used world-wide.

3.  Around the school, find the types of switches` listed in the following table. Type of switchWhat does the switch operate? Rocker switch Push button switch Pull switch Toggle switch

4.  Copy and complete the table in your notebook.  Choose 2 switches from your list. Explain how each one works and describe how they differ from each other.

5.  A switch controls the flow of electricity in a circuit. When you turn a switch on (close the switch), electricity can flow. When you turn it off (open the switch), you break the flow of electricity.

6.  Most electric devices contain switches. Sometimes they are easy to see and use, such as a light switch on the wall. Some switches are operated without being touched, such as an electronic switch that senses light levels or movement and turns on a light or opens the door at the grocery store. When you open a refrigerator door, a hidden switch turns on the light.

7.  There are many types of switched. A light switch on a wall is a rocker switch. A doorbell is a push button switch. A switch that is activated by pulling a chain is a pull switch. A switch that makes a light brighter or dimmer is a dimmer switch. A toggle switch is similar to a rocker switch.

8.  Some switches turn things on an off, while some switched can change the direction of a motor (like on a fan)  Circuit diagrams are used to show the parts of an electric circuit. Each part is drawn in a specific way, so that people around the world can understand them.  In circuit diagrams, wired are always drawn as straight lines, bends in the wire as 90 degree angles. Every electrical device has a symbol.