Introduction to Engineering and Technology Concepts

Unit Five

Chapter Four –

Electrical Energy

Instructions for Success:

• Each chapter of every unit will begin with a “Mindjog.” This is a warm up question that you should answer in your workbook in the proper chapter.

• Please take notes as you move through the presentations in the notebook that has been provided.

• Sections will come up in each presentation with an assignment notice. Turn to the section detailed on the slide in your workbook and complete the assignment before proceeding.

• Good luck!

Objective

• Students will define how electrical energy is harnessed and put into use.

Mindjog!

• On your worksheet, please respond to the following question: 

• “List the one piece of technology that you feel you could not live without. Does it require electricity to run…and if so, how does it get this electrical energy (battery, power cord, solar cells, etc.)?”

Electrical Energy

• In the Chapters dealing with energy, we said that electrical energy is associated with electrons moving along a conductor (Wright, 2004).

• In a previous chapter, we discussed that atoms have electrons and that electrons have a negative charge.

Electrons

Insulator

• When the electrons do not move within the atom, binding them in such a way, the result is an insulator.

• An insulator is a poor conductor of electricity.

• Items that are considered insulators include wood, plastic, glass, and so on (Brian,

2004).

Conductor

• Conductors, such as metals, allow the electrons to move within the atom.

• When the electrons move, it becomes easier for electricity to flow though the material.

• As the electrons move, they transmit electricity from one point to another (Brian, 2004).

Without a Conductor

• If no conductor of electricity is present, it cannot move and will never go from one point to the next (Brian, 2004).

Generators

• Using magnets, we can move electrons within an atom and go from point to point. Essentially, this is a generator.

• The generator’s job is to create a constant flow of electrons, including a specific amount of electrons and how fast they move (Brian, 2004).

Voltage/Amperage

• How fast those electrons flow is called voltage and the number of electrons flowing is called amperages .

• Traditionally, the terms are used as “volts” and “amps (Brian, 2004).”

Circuits

• Electrical circuits, regardless if they come from a battery or the wall socket, have common properties:

• There is always a positive and negative terminal.• The source of electricity will move electrons out of

the negative terminal at a certain voltage. • The electrons will move from negative to positive

through a proper conductor.• Attaching a load (radio, computer, light bulb, etc.)

in the middle of the circuit is how we deliver electricity to it (Brian, 2004).

Energy

• Consider that we use electrons because they move…they have energy…and energy is the ability to do work.

• Consider that in the winter, you use electrons because they can create heat, and heat will warm your home.

• Essentially, all electrical technology harnesses electrons and converts the energy into something useful (Brian, 2004).

Resistance

• Most power outlets in walls are delivering 120 volts of electricity.

• Using the idea of the heater from the last slide and a tool that can measure electricity, you’ll see that 10 amps is flowing from the wall outlet to the heater. That means that the heater is 1,200 watts.

• How did we come to this idea?• You multiply the volts times (X) the amps to get

your watts. 10 amps X 120 volts = 1,200 watts (Brian, 2004).

Resistance (continued)

• Now, if we think of resistance like a pipe that the electrons move through, it can increase or decrease to increase/decrease the flow.

• The basic equation for electrical engineering states that current is equal to voltage divided by distance (I=V/r).

• Say you have a 120 watt light bulb plugged into the wall socket. The voltage is 120, with 1 amp flowing through it. The filament is going to provide a resistance, which is found as r=V/I, or 120 ohms.

• What’s an ohm (Brian, 2004)?

Ohm’s Law

• George Simon Ohm formulated relationships among voltage, current, and resistance in this manner:

• The current in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the circuit.

• It is important to note that resistance cannot be changed by altering voltage or current (Molecular

Expressions: Electricity and Magnetism, n.d.).

Direct/Alternating Current

• Direct current (DC) means that the positive and negative terminals of the battery are always positive and negative and that current always flows in the same direction. Batteries are considered DC.

• Alternating current means that the current reverses 60 times per second (in the United States).

• With AC, it is easy to change the voltage using a transformer. Think about electricity coming from a power plant (Brian, 2004).

Grounding

• Electrical grounding, or ground, literally means the ground or the earth.

• The earth is a very good conductor of electricity and serves as a good return path for electrons (Brian, 2004).

Assignment #1

• Please turn to the section in your workbook entitled, “Unit Five, Chapter Four – Electrical Energy.”

• Complete the extension questions under the “Assignment #1” header before moving onto the next section of slides.

BEFORE MOVING ON:

• Did you complete the “Assignment #1” Section under the “Unit Five, Chapter Four – Electrical Energy” section of your workbook?

• If you have, please proceed to the next slide.

Chapter Four Completed!

• Please close this presentation and launch the file entitled, “Chapter 5 – Computer and Internet Connection.”

References

• Brian, M. (2004). How Electricity Works. Retrieved June 27, 2008 from http://science.howstuffworks.com/electricity.htm

• Molecular Expressions: Electricity and Magnetism (n.d.). Retrieved June 27, 2008 from http://micro.magnet.fsu.edu/electromag/java/ohmslaw

• Wright, R. (2004) “Technology” The Goodheart-Willcox Company, Inc.