Unit: Energy and Control- Electricity

 In January 1998, Ontario, Quebec, New Brunswick, and Nova Scotia were hit by the most sever ice storm in Canadian History. More than 1000 hydro transmission towers were pulled down by the weight of the ice and hydro poles were damaged. More than 3 million people lost electricity in their homes, some for many weeks.

 Do Activity 1 for homework. When you return to school with your list complete activity 2 and Draw table 2.1 in your notebook 2. Identify all the devices in your home that use electricity. Record these devices in the table. 3. For each device, record whether it operates wit batteries (direct current or DC), or with household current ( alternating current or AC). Note: Some devices plug into the wall (AC) but convert electricity into DC power. Look for those “boxy plugs” in your home and record them on your list at DC.

Electrical DevicesHow Many?Does the device use batteries (DC) or household current (AC) Light bulbs Clocks refrigerator AC 3DC, 1 AC AC

 How many electric devices do you have in your home?  Which devices do you use most often? Least often?  Which devices do you think use the most energy?

 Electronic devices change energy from one form into another.  Copy table 2.2 into your notebook and write the names of 10 devices from Table 2.1. Indicate the kinds of energy transformations that each electrical device makes. For example, a light bulb transforms electrical energy into both light energy and heat energy. Compare your table with your classmates

Name of Device Light Energy Sound Energy Heat Energy Mechanical Energy Other Light BulbXX

 Use the data from your table to make a bar graph. Use “form of energy” as the horizontal scale, and the “number of devices” on the vertical scale. Combine data with other students and make a group graph or even a whole-class graph. Display your graphs in the classroom.  On your graph, which energy transformation occurs most often? Write your answer in your notebook.  Think about all the devices from table 2.1. What is the most common energy transformation from electrical energy?

 Telephones use electricity to send signals through wires. Identify all devices from your list in Activity 1 that send or receive signals.  Copy table 2.3 in your notebook and complete it.

Name of deviceDoes it send receive, or both? TelephoneSend and receive

 How many devices do you have that send or receive signals?  Design a method to record how much time you spend each day using each of these devices.  On one page, explain the importance of electricity in your life. How does it compare with people’s use of electricity 50 years ago? 100 years ago? More than 100 years ago, how did people do things without electricity? What were the most common electrical devices 100 years ago?

 Can you imagine living without electricity? How would you see at night? How would your food stay cold? How would you cook it? And don’t bother watching TV or playing a video game! All these activities rely on electricity. Many electric devices were invented to make our lives easier, safer, and sometimes more fun.

 Electricity in the home became available only about 100 years ago. Many people did not have access to household electricity until recently. And people in some parts of the world do not have electricity in their homes.  When electricity flows we call it an electric current. There are 2 kinds of electric current. Direct current, or DC, is the electric current of batteries and generators. Battery- powered devices, such a flashlights or TV remote controls, use DC power. Many electronic devices, such as computers, also require DC power to operate. DC power is the electricity in electric vehicle such as subway trains, streetcars, trolley buses, and electric automobiles. Direct current electricity always flows in one direction.

 The main disadvantage of DC power is that wires cannot carry it efficiently over long distances. Therefore it is not carried through the wires that bring electricity into your home. Instead, alternating current, or AC, is the electricity in your wall outlets. AC electricity can be transmitted over long distances through wires. The AC electricity flow changes directions 60 times each second! This is called 60 cycles per second.

 Electrical energy is measured in volts. A D-sized battery has 1.5 volts of electrical energy. The wall outlet in your home has 120 volts.  Electricity all by itself is not very useful. However, it is very useful when it is changed, or “transformed” into another form of energy. Every electric device in your home transforms electricity into a more useful form of energy. The most common forms of transformed energy are light, sound, heat, and movement.

 However, some energy transformations are not needed. For example, you want the light bulb in your room to give you light only. But it warms up as well. You don’t need the heat, especially in the summer. Therefore, the heat from a light bulb is “wasted” energy.  When you turn on a flashlight, several energy transformations occur, called an energy chain. First, the chemical energy is converted into electrical energy. The electricity flows through a wire until it reaches the bulb. The electrical energy is then converted into light energy and heat energy.

 At every step in the chain, energy transformations lose energy, often as “wasted” heat energy. We need to use electricity wisely and save energy. For this reason, we want to use efficient devices: those that transform most of the electrical energy into the most useful form, without wasting any on nun-useful “waste: energy. Many devices have been invented that use electricity wisely. Many others waste electricity. You can probably find some devices in your home or school that use energy poorly.