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Software for Education and Industry


Electricity 101

Electricity 101 is an interactive computer program that will give you an intrinsic understanding of electricity through the use of text, graphics, animation, and sample problems.  No prior knowledge of electricity is assumed or required.  You can benefit from this program if...

Here is the Table of Contents of the program... 


Electricity 101

Table of Contents

              Chapter

            1.   Introduction

                        Why study electricity?

                        What do I care about electrons?

                        Where do I go from here?

              2.  What Is Electricity?

                        What is an electron?

                        What is a valence electron?

                        What makes a good conductor of electricity?

 

             3,  How Does Electricity Flow?

                        What makes electrons move?

                        How do electrons move?

                        Where do electrons go?

                        

             4.  How Is Electricity Made?

                        What are the 6 Categories of Electricity?

           

             5.  How Is Electricity Measured?

                        What is an amp?

                        What is a volt

                        What is resistance?

                        What is Ohm's Law?

                        What is a VOM?

                        How is a VOM connected to measure volts, amps, and ohms?

                        Sample Problems

      

             6. What is AC and DC?

                        What is DC?

                        What is AC?

                        What is Frequency?

                        What is Hertz?

                        What is RMS?

                        What is a Sinewave?

                        What is 3 Phase AC?

 

             7.  How Is Electricity Sold?

                        What are Watts? 

                        What are Kilowatt-Hours?

                        Sample Problems

       

             8.  What Are Some Types of  Circuits?

                        What is an Open Circuit?

                        What is a Short Circuit?

                        What is a Series Circuit?

                        What is a Parallel Circuit?

                        Sample Problems

        

             9.  How Is Electricity Made Safe?

                        How Much Electricity is Dangerous?

                        How Can We Protect Against Lightning?

                        How Can We Protect Against Short Circuits?

                        What Is a fuse?

                        What Is a Circuit Breaker?

                        What Is a GFCI?

                        What Is an AFGI?

                        Why are some wires bigger than others?

              

             10.  How is My House Wired?

                        What is a transformer?

                        What is a panelboard?

                        What is a single-pole breaker?

                        What is a two-pole breaker?

                        Why doesn't that bird get electrocuted?

                        

              Index

 

              About the Author


Electricity 101 is written in .html format so you can use your favorite internet browser to navigate through it using hyperlinks, bookmarks, and word searches.  Electricity 101 requires no software installation on your computer.  Just double-click on the Table of Contents.html.

Electricity 101 is written by a Professional Engineer with 14 years industrial experience and 20 years experience teaching electrical engineering technology at the college level.

Following are some sample screens shots from Electricity 101...


...part of Chapter 5.  How Is Electricity Measured?

The next picture shows a VOM connected to check for "continuity".  The meter is placed in the Ohm reading position, usually on the most sensitive (smallest resistance) scale.  A continuity test is performed to determine if there is a continuous path for electricity to flow between two points.   This is useful, for instance, to trace a wire in a circuit, to check if a wire is broken, to check if contacts are closed, or to check if a fuse is blown.  

If the wire, contact, or fuse is intact, the VOM will read virtually zero ohms, since a piece of wire, good contact, or good fuse has very little resistance.   You would get the same result if you touched the two leads of the meter together.

If the wire, contact, or fuse  is broken, the VOM will read extremely high resistance because the air gap at the break has very high resistance.  The extremely high resistance is usually indicated by "O.L." on a digital meter, meaning "overload", because the resistance is higher than the meter can indicate.  You would get the same result if you simply held the two leads apart in the air, since the resistance of air is very high (i.e.: air is not a very good conductor of electricity, except in the presence of an extremely high voltage such as lightning or a high voltages arc).


...part of Chapter 9.  How Is Electricity Made Safe?

What is a Ground Fault Circuit Interrupter (GFCI)?

There are some electrical faults that a fuse or circuit breaker cannot protect against.  For instance, fuses and circuit breakers in a home usually have a 15 amp or 20 amp current rating.   An electrical circuit may have a small "leakage" current to ground, called a "ground fault", that is not enough current to trip the fuse or circuit breaker.  But if you get in the path of the leakage current it can travel through your body on the way to ground and cause injury or death.  We saw in the table at the beginning of this chapter that a current as low as 0.075 amps can cause heart fibrillation.  The chances of the leakage current passing through you to ground is increased if you are in contact with water, thereby decreasing your resistance to ground.  For this reason, devices called Ground Fault Circuit Interrupters (sometimes just called Ground Fault Interrupters or GFIs) are required by the National Electrical Code in locations where water is present, like bathrooms or outdoor receptacles.

Ground Fault Circuit Interrupters can be built into convenience outlets, circuit breakers, or portable power cords for use on construction sites as shown below.

Regardless of their packaging, GFCI's work by comparing the amount of current that flows from the receptacle or circuit breaker to the load with the amount of current that flows back from the load.  If the two currents don't match, then some current must be leaking to ground through a ground fault, and the GFCI trips to remove power from the circuit.

It is interesting to note that some motor driven equipment like freezers are exempt from GFCI requirements because they inherently have leakage current to ground, and use of a GFCI would result in nuisance trips.


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