The links below provide an outline of the material for this lesson. Be sure to carefully read through the entire lesson before returning to Canvas to submit your assignments.
It looks like we are ready to go for lesson 1: Energy and Society. This lesson is going to teach us basically about energy. What is energy, and with which units do we measure energy? We will learn about the commonly used units we use to measure energy. There are different forms of energy that we use; for example, we use electrical energy or mechanical energy, like moving a car, etc., and we need to know the units in which we measure these different forms of energy. So we will also learn about forms of energy. We will learn about the units in which we measure these forms of energy, and also we will get into a very, very important distinction between energy and power. To be clear, that is the key concept in this lesson that I want you to concentrate on – power and energy. And once we know the difference, we know that using power, we can calculate energy, or if we know the energy and time, we can calculate power.
We will also look at some of those calculations. As I said, once we know the power, we can calculate the energy, so we are going to do some exercises. For example, a computer consumes some power, the rate at which energy is drawn, and if we use the computer for so many hours, what is the energy consumption by this computer? We can do the same thing for a refrigerator, or we can do it for any other appliance that you use at home. These are common appliances that we are using every day in our lives. When we add up the energy consumed by a computer, by a toaster, by an oven, by a refrigerator, by lighting, etc. at your place, you get, basically, energy consumption of all your equipment for a day. So we are going to do that and calculate energy consumption for a day, and then for a month, and we can calculate also the electric bill for one whole month -- that would be our objective in this lesson.
Be careful, again, because the distinction between energy and power is a very important concept. Forms of energy and the units in which we measure energy are the concepts that we will be looking at in this wonderful lesson. All Right! Why Wait? Let’s go and start our lesson.
Good Luck!
When thinking about energy the following questions may come to mind:
Energy is the life blood of any modern society. Energy is used in every walk of life. Without it, modern life would almost come to a standstill. From the moment of waking up in the morning with an alarm clock, we use energy for almost everything we do.
Energy is a property of matter that can be converted to work, heat or radiation. It can move things or do work, produce heat even if it does not move anything, and be converted to light (or more accurately, radiation).
Upon completing this lesson, you should be able to:
Step | Activity | Access / Directions |
---|---|---|
1 | Read the online lesson | Lesson 1 - Energy Supply and Demand |
2 | Watch | Lesson 1 - Guided Review (Flash movie) (a printable Review Sheet is also provided) |
3 | Read | Lesson 1 - Questions for Review and Discussion |
4 | Review | Lesson 1 - Resources (supplemental materials that are optional...but informative!) |
5 | Complete | Lesson 1 - StudyMate Activities (You will obtain feedback for these exercises, but they will not count toward your final course grade.) |
6 | Take | Lesson 1 - Quiz (graded) The quiz is available in Canvas. |
Please refer to the Calendar in Canvas for specific timeframes and due dates.
If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way you might help a classmate!
Energy exists in a number of different forms, all of which measure the ability of an object or system to do work on another object or system. There are six different basic forms in which we use energy in our day-to-day life:
A book sitting on a shelf in the library is said to have potential energy because if it is nudged off the shelf, gravity will accelerate the book, giving the book kinetic energy. Because the Earth's gravity is necessary to create this kinetic energy, and because this gravity depends on the Earth being present, we say that the Earth-book system is what really possesses this potential energy, and that this energy is converted into kinetic energy as the book falls.
The glucose (blood sugar) in your body is said to have "chemical energy" because the glucose releases energy when chemically reacted (combusted) with oxygen. Your muscles use this energy to generate mechanical force (work) and also heat.
A hot cup of coffee is said to possess "thermal energy," or "heat energy," because it has a combination of kinetic energy (its molecules are moving and vibrating) and potential energy (the molecules have a mutual attraction for one another) - much the same way that the book on the bookshelf and the Earth have potential energy because they attract each other.
All matter is made up of atoms, and atoms are made up of smaller particles called protons (which have positive charge), neutrons (which have neutral charge), and electrons (which are negatively charged).
In both fusion and fission, some of the matter making up the nuclei is converted into energy, represented by the famous equation:
$${\text{E=mc}}^{\text{2}}$$ $$\text{Energy=Mass}\times {\left(\text{SpeedofLight}\right)}^{2}$$Photons are created when electrons jump to lower energy levels in atoms, and are absorbed when electrons jump to higher levels. Photons are also created when a charged particle, such as an electron or proton, is accelerated. An example of this phenomenon is a radio transmitter antenna that generates radio waves.
Please watch the following 3:20 video about the electromagnetic spectrum:
As depicted in the image above, the lower the energy, the longer the wavelength and lower the frequency, and vice versa.
The reason that sunlight can hurt your skin or your eyes is because it contains "ultraviolet light," which consists of high energy photons. These photons have short wavelength and high frequency, and pack enough energy in each photon to cause physical damage to your skin if they get past the outer layer of skin or the lens in your eye.
Radio waves, and the radiant heat you feel at a distance from a campfire, for example, are also forms of electromagnetic radiation, or light, except that they consist of low energy photons (long wavelength and high frequencies - in the infrared band and lower) that your eyes can't perceive. This was a great discovery of the nineteenth century - that radio waves, x-rays, and gamma-rays are just forms of light, and that light is electromagnetic waves.
About 20% of the electricity used in the US is used to produce visible light for lighting purposes.
Can you identify the different forms of energy in the picture below? Enter your answer in the table below and click the "Check Answers" button to check your work.
These things, listed below, represent the six fundamental forms of energy: Mechanical, Chemical, Thermal/Heat, Electrical, Nuclear and Radiation. Your task is to determine what form of energy is represented by each item.
Now spend some time trying to identify the different forms of energy that are at work in the above items. Once you have thought through this and have some answers, read on to see if you are correct.
AnswersLight bulb in a lamp post - Electrical Energy
Cups of water. One is sitting on a table and the other is in a woman's hand. - Thermal or Heat Energy
An X-ray - Nuclear Energy
A Frisbee flying through the air - Mechanical (kinetic) Energy
The sun - Radiation
A golf club getting ready to hit a ball - Mechanical (Potential)
The ice cream in an ice cream cone - Chemical
Energy can be converted from one form to another.
Examples:
Most of the day-to-day devices that we use are energy conversion devices. In this activity, you will identify the fundamental form of energy that is put in to each device and the output form of energy that is a result.
Your task is to look at six devices and decide what form of energy is the input and which is the output form of energy. Think about your answers carefully before reading ahead to the answers.
Device | Input form of Energy | Output form of energy | |
---|---|---|---|
1 | Lawn Mower | Chemical | Mechanical or kinetic |
2 | Computer | Electrical | Light and Sound |
3 | Sun | Nuclear | Radiant |
4 | Tree | Radiant | Chemical |
5 | Gas Furnace | Chemical | Thermal or Heat |
6 | Hair Dryer | Electrical | Heat or Electric |
How is energy measured? It is measured in various units by various industries or countries in much the same way as the value of goods is expressed in Dollars in the U.S. and Yen in Japan and Pounds in Britain.
The table below identifies different units for measuring energy.
Unit | Definition | Used In | Equivalent to |
---|---|---|---|
British Thermal Unit BTU | A unit of energy equal to the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. Equivalent to energy found in the tip of a match stick. | Heating and Cooling industries | 1 BTU = 1055 Joules (J) |
Calorie or small calorie (calorie) | The amount of energy needed to raise the temperature of one gram of water by one degree Celsius. | Science and Engineering | 1 calorie = 0.003969 BTUs |
Food Calorie, Kilocalorie or large calorie (Cal, kcal, Calorie) | The amount of energy needed to raise the temperature of one kilogram of water one degree Celsius. The food calorie is often used when measuring the energy content of food. | Nutrition | 1 Cal = 1000 cal, 4,187 J or 3.969 BTUs |
Joule (J) | It is a smaller quantity of energy than calorie and much smaller than a BTU. | Science and Engineering | 1 Joule = 0.2388 calories and 0.0009481 BTUs |
Kilowatt Hour (kWh) | An amount of energy from the steady production or consumption of one kilowatt of power for a period of one hour. | Electrical fields | 1 kWh = 3,413 BTUs or 3,600,000 J |
Therm | A unit describing the energy contained in natural gas. | Home heating appliances | 1 therm = 100,000 BTUs |
When writing BTUs, one uses a base of “10” raised to a particular exponent.
For example:
More specific notation involves the following:
To express measurements greater than those with a base of 10, you would do the following:
The presentation below shows the energy used by various countries or processes on a logarithmic scale as measured in BTUs. Please watch the following 4:08 video:
Ok. What we are looking at here is energy scale. Energy scale basically gives us different things. Or it puts different energy consumptions in perspective. For example, a BTU is defined as energy required to raise the temperature of one pound of water through one degree Fahrenheit. This is a small amount of energy. It is one single BTU. That is the unit. It is like a dollar. A dollar can buy you certain things. And when somebody says I bought 10 pencils immediately it strikes you that it is roughly about a dollar or so. If somebody says “I bought a computer” you immediately think about thousands of dollars; a thousand or two, and so on. If somebody says “I bought a car today” which means 10’s of thousands of dollars. Similarly, somebody buys a home. It is 100’s of thousands or dollars. It could be one hundred thousand, it could be two hundred thousand, it could be three hundred thousand. And so on. That is the scale that we are looking at here.
We know on the energy scale 1 BTU is the basic unit. On the same scale if you look at average daily human food intake is about 10,000 BTUs and in a gallon of gasoline we have about 100,000 BTUs or even slightly higher. What that tells you is that a gallon of gasoline can basically provide a human being with 10 days worth of supply of food intake or the same number of BTUs basically, or calories in other words. So technically we can survive with one gallon of gasoline or the equivalent number of BTUs for about 10 days - a human being. Similarly, everyone in the world consumes about 65 million BTUs annually. World per capita annual energy consumption is roughly about 65 million BTUs per person so every person is consuming 65 million BTUs a year.
If you compare that with the United States per capita consumption that is about 300 million BTUs or slightly over that actually, per year per person .Which means that in the United States, every one of us is consuming roughly 5 times than what an average person in the world would consume - energy wise. And on the same scale, we can compare different things.
This is total annual energy consumption by the United States, as a country, the whole country, which is roughly about 100 Quadrillion BTUs. A Quadrillion BTUs is 10 to the 15. A quadrillion BTUs is 10 raised to the 15 which is a thousand trillion.
Similarly, if you look at here, world per capita energy consumption, that is about roughly 400 Quadrillion BTUs, which is 4 times the Unites States energy consumption. To put things in perspective, what we can say is that the United States consumes about ¼ of the entire worlds energy. And we say we are consuming a lot of energy and the world is consuming a lot of energy, but look at this here. Look at this. Annual energy that is reaching from the sun, free of cost is roughly 10 to the 22 which is kind of 22 to 23 thousand times more than what the entire world consumes today in a year.
Then, I want you to think about this. Why are we worried about energy? If we are getting 22 thousand times more than what we consume, free of cost, every year, then why are we worried about energy? Think about that.
It is interesting to note that the earth received 24,330 times more energy than the entire world used in 2001. Then one might ask, “Why should anybody worry about energy shortage?" Whether energy is there or not is actually a secondary concern. The real issue is the form in which the energy is available and whether it can be easily converted to the form that we need.
Energy is stored and is available in different forms and sources. The 24,330 times more solar energy that is available than we need is not in a readily usable form. It needs to be concentrated.
For example, when oil (a concentrated fuel) is burned with air, the resulting gases can reach high temperatures. Solar energy, as it is, is not concentrated and cannot reach those high temperatures. Therefore, we use more concentrated energy sources. These sources are divided into two groups—renewable and nonrenewable.
They're called fossil fuels because they were formed over millions and millions of years by the action of heat from the Earth's core and pressure from rock and soil on the remains (or 'fossils') of dead plants and animals.
Fossil fuels, non-renewable energy sources formed over a million years, are not distributed uniformly over the earth’s surface. Depending on the climate conditions millions of years ago, certain parts of the land masses were favorable for organic matter to grow and thrive.
Over geological ages, these land masses moved, and certain regions are richer in fossil fuels than others. Roll over the map below and answer click to answer the questions based on your observations.
The most abundant resources for various global regions are as follows:
The activity below is a drag and drop. Select the items listed in the center of the image and drag them to the corresponding or matching energy type listed on the side.
Click the "play" button below and observe what happens.
Both cyclists did the same amount of work (they both pedaled 10 miles), and used the same amount of energy (218 calories). The blue cyclist, however, demonstrated the most power, because he did the equivalent amount of work as the red cyclist, but in a faster time.
Power is the rate at which we do work.
Energy is the capacity to do work.
Work is the amount done.
Units of Power are not the same as units of energy (i.e., Btus, calories). Units of power are measured in terms of units of energy used per some unit of time.
Examples of Units of Power include:
Power can be determined by the following formula:
$$\begin{array}{l}\text{Power}=\text{Energy}\left(\text{orwork}\right)\text{}/\text{Time}\\ \text{or}\\ \text{Energy}=\text{Power}x\text{DurationofUsage}\left(\text{Time}\right)\end{array}$$On a winter day, a home needs 1 x 10^{6} or 1,000,000 BTUs of fuel energy every 24 hours to maintain the interior at 65° F. At what rate is the energy being consumed in Watts?
$$\begin{array}{l}Power(Watts)=\left(1\times {10}^{6}Btus/24h\right)\\ \\ =1,000,000\text{}Btus/24\text{}h\\ \\ Power(J/s)=\frac{\left(1,000,000\text{}Btus\times 1,055\text{}J/s\right)}{\begin{array}{l}\left(24h\times 3,600s\right)\\ \\ =12,200(rounded\text{}number)\end{array}}\end{array}$$If 1 J/s = 1 Watt, and 1000 Watt = 1kW, then 12,200 J/s = 12,200 Watts = 12.2 kW
To solve this problem, you must realize the following: You know the Power (1,000,000 BTUs/24 hours) and the time (24 hours), so you need to solve for Energy. The measurements must be consistent, so the BTUs should be converted to a consistent measure, such as Joules:
$$1\text{}Watt\text{}=\text{}1\text{}J/s\text{}and\text{}1\text{}BTU\text{}=\text{}1,055\text{}J$$If using Joules per second instead of watts, you must convert 24 hours into seconds or divide it by the number of seconds in an hour (3600).
Image Credit: © Penn State University, is licensed under CC BY-NX-SA 4.0 [3]
We can also use a version of the Power formula to determine Cost of Energy:
$$\begin{array}{l}\text{EnergyUse}=\text{Power}\times \text{TimeofPowerUse}\\ \text{CostofEnergy}=\text{EnergyUsed}\times \text{CostoftheUnitofEnergy}\end{array}$$If a 100 W light bulb is accidentally left on overnight (8 hours), how much energy does it consume?
$$\begin{array}{l}\text{EnergyUse}=\text{Power}\times \text{TimeofPowerUse}\hfill \\ \text{EnergyUse}=\text{}100W\text{}\times \text{}8h\text{}=\text{}800Wh\text{or}0.8kWh\hfill \end{array}$$How much energy does this cost, if electricity costs 10 cents per Kilowatt?
$$\begin{array}{l}\text{CostofEnergy}=\text{EnergyUsed}\times \text{CostoftheUnitofEnergy}\hfill \\ \text{CostofEnergy}=\text{}.8kWh\text{}\times \text{}10\text{cents}=\text{}\$0.08\hfill \end{array}$$How is energy use of Home Appliances calculated?
You just learned in a previous discussion on power that:
or
$$\text{Energy}=\text{Power}\times \text{DurationofUsage}\left(\text{Time}\right)$$By modifying this formula slightly, we can determine Energy Consumption per Day:
Where:
Since we want to measure Energy Consumption in Kilowatt hours, we must change the way Power Consumption is measured from Watts to Kilowatts (kWh). We know that 1 kilowatt hour (kWh) = 1,000 Watts hours, so we can adjust the formula above to:
If you use a ceiling fan (200 watts) for four hours per day, and for 120 days per year, what would be the annual energy consumption?
Use this formula:
$$\begin{array}{l}\text{EnergyConsumption/Day}\left(\text{KWh}\right)\text{}=\hfill \\ \text{PowerConsumption}\left(\text{Watts/1000}\right)\text{}\times \text{HoursUsed/Day}\hfill \end{array}$$ $$\text{EnergyConsumptionperDay}\left(\text{kWh}\right)\text{}=\text{}\left(200\text{}/1000\right)\text{}\times \text{}4\text{}\left(\text{hoursusedperday}\right)$$ $$\text{EnergyConsumptionperDay}\left(\text{kWh}\right)\text{=}\left(\text{1/5}\right)\text{}\times \text{4EnergyConsumptionperDay}\left(\text{kWh}\right)\text{=4/5or.8}$$So the Energy Consumption per Day is .8 kWh To find out energy for 120 days, do simple multiplication: .8 x 120 = 96 kWh
If the price per kWh for electricity is $.0845, what is the annual cost to operate the ceiling fan?
$$\begin{array}{l}\text{AnnualCost}=\text{AnnualEnergyConsumption}\left(\text{KWh}\right)\text{}\times \text{priceperKWh}\\ \text{AnnualCost}=\text{}96kWh\text{}\times \$.0845/kWh\text{}=\$8.12\end{array}$$If you use a personal computer (120 Watts) and monitor (150 Watts) for four hours per day, and for 365 days per year, what would be the annual energy consumption?
$$\begin{array}{l}\text{EnergyConsumption/Day}\left(\text{kWh}\right)\text{}=\text{}\left(270/1000\right)\text{}\times \text{}4\text{}\left(\text{hoursused/day}\right)\text{}\\ \text{EnergyConsumptionperDay}\left(\text{kWh}\right)\text{}=\text{}1.08\end{array}$$So the Energy Consumption per Day is 1.08 kWh. To find out energy for 365 days, do simple multiplication:
$$1.08\text{kWh}\times \text{}365\text{days}=\text{}394.2\text{kWh}$$The annual cost if electricity is $0.0845 per kWh would be:
$$\text{Cost}=\text{}394.2\text{}kWh\text{}\times \$.0845/kWh\text{}=\$33.30$$What is the energy consumption of a refrigerator with a wattage rating of 700 Watts when it is operated for 24 hours a day?
To solve, use the following formula:
$$\text{EnergyConsumption=PowerConsumption}\times \text{NumberofHoursOperated}$$Where:Energy Consumption = Watt/Hours (Wh) or KiloWatt/Hours (kWh)
Power Consumption = Watts (W) or kW (KiloWatts)
Number of Hours Operated = Hours (h)For the example above:
Energy Consumption = 700 W x 24 h
Energy Consumption = 16800 W/h
To convert from W/h to kWh/h, remember that 1kWh/h = 1000 W/h
To solve, set up as a ratio and use linear algebra to solve for ?.
$$\begin{array}{l}\begin{array}{ccc}\frac{1\text{}kWh}{1000\text{}Wh}& =& \frac{?kWh}{16800\text{}Wh}\\ \frac{16,800\text{}Wh\left(1\text{}kWh\right)}{1000\text{}Wh}& =& ?KWh\\ 16.8\text{}KWh& =& ?KWh\end{array}\\ \end{array}$$Use the following link to generate a random practice problem [4].
You can usually find the wattage of most appliances stamped on the bottom or back of the appliance, or on its "nameplate." The wattage listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for example, the volume on a radio), the actual amount of power consumed depends on the setting used at any one time.
A refrigerator, although turned "on" all the time, actually cycles on and off at a rate that depends on a number of factors. These factors include how well it is insulated, room temperature, freezer temperature, how often the door is opened, if the coils are clean, if it is defrosted regularly, and the condition of the door seals.
To get an approximate figure for the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three.
The table below shows wattage of some typical household appliances.
Appliance | Wattage (range) |
---|---|
Clock Radio | 10 |
Coffee Maker | 900 - 1200 |
Clothes Washer | 350 - 500 |
Clothes Dryer | 1800-5000 |
Dishwasher | 1200-2400 |
Hair Dryer | 1200-1875 |
Microwave Oven | 750-1100 |
Laptop | 50 |
Refrigerator | 725 |
36" Television | 133 |
Toaster | 800-1400 |
Water Heater | 4500-5500 |
Appliance | Wattage |
---|---|
Aquarium | 50 - 1210 |
Clock Radio | 10 |
Coffee Maker | 900 - 1200 |
Clothes Washer | 350 - 500 |
Clothes Dryer | 1800-5000 |
Dishwasher | 1200 -2400 (using the drying feature greatly increases energy consumption) |
Dehumidifier | 785 |
Electric Blanket - Single/Double | 60 / 100 |
Fan - ceiling | 65 - 175 |
Fan - window | 55 - 250 |
Fan - furnace | 750 |
Fan - whole house | 240 - 750 |
Hair Dryer | 1200 - 1875 |
Heater (portable) | 750 - 1500 |
Clothes Iron | 1000 - 1800 |
Microwave Oven | 750 - 1100 |
Personal Computer - CPU - awake / asleep | 120 / 30 or less |
Personal Computer - Monitor - awake / asleep | 150 / 30 or less |
Laptop | 50 |
Radio (stereo) | 70 - 400 |
Refrigerator (frost free, 16 cubic feet) | 725 |
19" Television | 65 - 110 |
27" Television | 113 |
36" Television | 133 |
53" - 61" Projection TV | 170 |
Flat Screen TV | 120 |
Toaster | 800-1400 |
Toaster Oven | 1225 |
VCR / DVD | 17 - 21 / 20 - 25 |
Vacuum Cleaner | 1000 - 1440 |
Water heater (40 gallon) | 4500 - 5500 |
Water pump (deep well) | 250 - 1100 |
Water bed (w/heater, no cover) | 120 - 380 |
If the wattage is not listed on the appliance, you can still estimate it by finding the current draw (in amperes) and multiplying that by the voltage used by the appliance.
Most appliances in the United States use 120 volts. Larger appliances, such as clothes dryers and electric cooktops, use 240 volts. The amperes might be stamped on the unit in place of the wattage.
If not, find an ammeter to measure the current flowing through it. You can obtain this type of ammeter in stores that sell electrical and electronic equipment.
Take a reading while the device is running; this is the actual amount of current being used at that instant.
Also note that many appliances continue to draw a small amount of power when they are switched "off."
These "phantom loads" occur in most appliances that use electricity, such as VCR, televisions, stereos, computers, and kitchen appliances.
Most phantom loads will increase the appliance's energy consumption a few watts per hour. These loads can be avoided by unplugging the appliance or using a power strip and using the switch on the power strip to cut all power to the appliance.
Watch the Lesson 1 Review below.
For more information on topics discussed in Lesson 1, see these selected references:
The following practice exercises are designed to help you assess your readiness for the Lesson 1 quiz. Neither activity is graded and you can attempt these activities as many times as you like.
Try them out and see how well you do!
You must complete a short quiz that covers the reading material in lesson 1. The Lesson 1 Quiz can be found in the Lesson 1: Energy and Society module in Canvas. Please refer to the Calendar in Canvas for specific time frames and due dates.
Links
[1] https://www.e-education.psu.edu/egee102/sites/www.e-education.psu.edu.egee102/files/files/lesson1/energy_conversion_LD.html
[2] https://commons.wikimedia.org/wiki/File:BlankMap-World-v2.png
[3] https://creativecommons.org/licenses/by-nc-sa/4.0/
[4] https://courseware.e-education.psu.edu/courses/egee102/L01Instruction/activity/check012701.html
[5] https://www.flickr.com/photos/90494562@N05/8222743554/
[6] https://www.flickr.com/
[7] https://creativecommons.org/licenses/by/2.0/
[8] http://www.eia.doe.gov/kids/energyfacts/index.html
[9] http://www.eere.energy.gov/consumer/