Chapter 6: Electric Energy at Home

Unit B: Energy Transformations

6.1 Generating Electric Energy A generator is a device that makes electricity.

Michael Faraday made the first electric generator in the early 1800s.

Pushing a magnet through a coil of wire generates an electric current, more coils and stronger magnets produce more electric energy.

The large amounts of electricity that we use today are produced by gigantic generators.

Input Energy

GeneratorKinetic Energy

Output Energy

Converter

Electric Energy

6.2 Generating and Distributing Electric Energy Most electricity is made in a generator. Generators

contain one or more turbines. As the blades of the turbines turn, their kinetic energy is

transformed into kinetic energy in the generator. This is what produces energy. See figure 6.5 on Pg 102

Hydro-electric: converts kinetic energy of moving water into electric energy

Thermo-electric: converts chemical energy stored in fossil fuels into thermal energy, then to kinetic energy, then to electric energy

Thermonuclear: splits atoms, releasing thermal energy that is converted to kinetic energy, then to electric energy

6.2 Generating and Distributing Electric Energy (Continued)

Coal-fired thermo-electric plants burn coal to generate electric energy. The smoke from burning the coal is put through scrubbers to remove the harmful chemicals. See Figure 6.8 on Pg 104

What are the advantages and disadvantages of using fossil fuels like coal, petroleum, and natural gas?

6.2 Generating and Distributing Electric Energy (Continued)

Hydro-electric plants produce much of the electric energy in Canada.

Kinetic energy from falling water is used to generate electric energy

Clean, efficient/little maintenance, little environmental damage, and no emissions

Require large dams which change the ecology of the area

6.2 Generating and Distributing Electric Energy (Continued)

Thermonuclear generation stations split uranium atoms using nuclear fission. This releases a large amount of thermal energy. The energy is then used to make steam and the steam, under pressure, turns a turbine. See Figure 6.9 on Pg 106

What are the advantages and disadvantages of nuclear energy?

6.2 Generating and Distributing Electric Energy (Continued)

Thermonuclear and thermo-electric plants are sometimes located close to cities. This lessens the distance to transmit the power, but creates environmental issues.

Electricity must be transmitted through power lines to get to the communities they serve. About 10% of the electricity is converted to thermal energy and wasted.

Power lines can also cause problems because heavy storms may cause damage to the power lines and it could take weeks to repair.

6.3 Electric Energy and Power Energy is the ability to do work.

Work is defined by force (F) multiplied by distance (d) over which the force is applied.

Work = F × d The joule is the unit used in measuring work.

Force is measured in newtons. When a newton of force is applied for one meter of

distance (1 N × m), one joule of work is done.

Power is the rate at which energy is transferred. Power tells how fast energy is used or produced. If a machine useds one watt of power, it uses one

joule of energy in one second.

6.3 Electric Energy and Power (Continued)

The consumption of electric energy is measured in watts. The watts are multipled by the time it takes to use them. Energy = power × time 1 watt hour (W×h) = 1 watt × hour

The watt hour is a small unit of energy. Electiric utility companies use a unit of energy 1000 times larger. One kilowatt hour is equal to 1000 watt hour kW×h

6.4 Efficiency and Saving Energy Incandescent light bulbs produce light when

electricity flowing through the filament makes the thin wire white hot.

Efficiency is a measure of how completely input energy is converted to accomplish the desired output energy. Incandescent light bulbs produce more heat than

flourescent bulbs, so flourescent bulbs are more efficent. Percent efficiency of an electric device = useful energy

output × 100 total electric enrgy input

6.4 Efficiency and Saving Energy (Continued)

Efficiency is important to you and the environment.

You: Use less electricity, save on your monthly utility bill.

Environment: Electricity is generated by fossil fuels. As coal burns, it produces carbon dioxide, sulfur

dioxide, and nitrous oxide gases. These are released into the atmosphere and harmful emissions. Carbon dioxide is linked to global climate

change. Sulfur dioxide and nitrous oxides are the primary

causes of acid deposition.