Electricity: History and Facts

Following is the script in question-answer form that I used to talk about electricity in a 4th-5th grade class. For high school classes more details and higher level concepts should be included.

Anil Pahwa

Professor

Electrical and Computer Engineering

Kansas State University

Tel: 785-532-4654

E-Mail: pahwa@ksu.edu

Personal Webpage

Q. Is there anyone in the room who can live without electricity?

Of course not. Because without electricity you will not be able to watch TV, play on the computer, or read your favorite book in the night. You may use candle to read, but it won't be very comfortable. There are some people still living who didn't have electricity when they were young and thus, they had to use candle to read.

(Turn the lights off in the room for dramatic effect)

Q. How is electricity made?

In most cases mechanical motion is used to make electricity. A turbine operated by steam, water or wind rotates a generator to make electricity. Heat for heating water to make steam is obtained by burning coal, oil, or gas or by nuclear fission. Generator has magnets which create electricity when rotated.

(Show demonstration of generator and motor built from a kit)

Q. When was electricity made available to people for the first time? By whom?

On September 4, 1882 Thomas Edison opened the Pearl Street Station in New York City to provide electricity to 85 rich customers and their 400 lamps in a one square mile area. The electricity was made by DC generators.

Q. What is DC and what is AC?

DC - Direct Current. Does not change.
AC - Alternating Current. Goes up and down like a roller-coaster.
Most of the electricity used by people today is AC.
Batteries provide DC.

(Walk in a straight line for DC and zig-zag for AC)

Q. Why is it that the power people receive at home is AC?

DC was very lazy. It didn't want to go too far. Therefore, George Westinghouse worked on AC. He was able to make AC travel 30 miles soon after Edison opened the Pearl Street Station. In 1893 his company provided power to the Columbia Exposition in Chicago.

Q. How far does AC travel today?

Thousands of miles. If you were able to enter the plug in your room you will be able to get to the top of the Empire State building or to Disney World for example. (Please don't play with the plug in your room. It is very dangerous.) The system is a big complex maze of wires.

(Show map of a Power Pool)

Q. How big?

The system has approximately 600,000 miles of high voltage transmission lines and 2.5 million miles of distribution lines. Highest voltage level in USA is 765,000 Volts. Total generation capacity in USA* is 735 Giga Watts which is 735,000,000,000 Watts and total electricity consumption per year in USA* is 2,810,000,000,000,000 Watt-hours.

Electricity consumed per person in a year in the USA is approximately 1000 times that in many countries, such as India.

* 1990 figures

Q. What is the voltage and frequency of power supply in your home?

120/240 Volts and 60 Hertz or cycles/second. The voltage goes up and down 60 times in a second.

Q. How much power a light bulb in the house requires.

An average light bulb needs 40 to 100 Watts.

Q. What is the cost of electricity?

1 kWh which is 1000 Watt-hours cost 7¢ approximately. At this rate the cost of electricity to operate a 100 Watt bulb for 2 hours is 1.4¢.

Q. What will happen when we run out of fossil fuels?

We have to look for alternative sources for generating electricity, such as solar power and wind power. Also, to delay depletion of fossil fuels we should reduce consumption of electricity and conserve energy.

Q. How do we conserve energy?

Turn off lights when you are not in a room. Although it doesn't cost much to operate light bulbs, the accumulated effect can be large. Decrease temperature setting of heater and increase temperature setting of air conditioner.

Q. How much energy will you consume if you are reading under a light which has a lamp of 75 Watts and you take 45 minutes to read the book? How much will it cost?

Bibliography

1. Jim Collins, "The Power Grid," US Airways Attaché, Nov. 1997, pp. 43-45.
2. "Thomas Alva Edison and Electric Power Engineering," IEEE PES Publication, Piscataway, NJ, 1997 (http://www.engine.ieee.org/power/edison.htm).
3. J.D. Glover and M. Sarma, "Power System Analysis and Design," 2nd Edition, PWS Publishing Co., Boston, MA, 1994.

Pictures