To: Rupert Giles, Public Relations Director, Awesome Electric Company From: Peter Dimpfl, Project Engineer, Awesome Electric Company Date: June 28, 2008 Subject: The Technical Meaning and Use of Joules in Awesome Electric As you requested, this is the memo addressing the definition of a joule. This memo should assist you in understanding the term and explaining it to the general public. I have included the cause of our precarious dilemma. Additionally, I provide a clear and concise definition of the term, joule and real world examples are added to enhance the definition and provide further explanation.
Our Current Situation
This section summarizes our current situation and provides the background why joule was misinterpreted by the public. In a speech given in our previous summer press conference for energy efficiency, one of our public relations representatives misstated the energy requirements for one of our new turbines used in the power plant. During the speech, the representative’s goal was to explain the company’s newly purchased, energy-efficient turbine which produced the same amount of energy as previous models but required less input energy to function. He did an excellent job in his explanation except for one occasion when he used the wrong terminology. Not knowing much about the actual manner in which energy is produced or the terminology involved, he decided to get expert help. He went to the engineers in charge of the turbine to get actual numbers and terms he could use to make his speech more impressive and fact based. The engineers told him the exact energy figures that the turbine required producing the necessary amount of power. On a piece of scratch paper he recorded, 50 million joules and 30 million watts. The engineers specifically told him to use the wattage for his speech and, if need be, the joules for questioning. Thinking he would remember this advice, he set the piece of paper aside for a few days. As it would happen, he failed to remember the engineers’ advice. On the day of the press conference, he only added the 50 million joules into his speech. When he gave the conference, he told the public that “The new turbine only needs 50 million joules to produce enough energy to provide energy our customers for a week.” The problem with this statement is when the word joule is pronounced, it sounds the same as jewel. He failed to realize that the two are homophonic. Since he failed to explain the method in which energy was produced, non-scientific individuals and the majority of the general public took this statement at face-value. The turbine needs 50 million jewels to produce the necessary energy!
Immediately following this speech, outraged people called our customer service lines causing mass confusion and the exhaustion of our staff. It seems they thought that our use of so many jewels would corner the market and drive up prices of individual luxury items. Also, thinking that we had priority over the jewels, various jewelers threatened legal action against us. In order to help solve this dilemma, a good place to start is to give a clear definition of what a Joule is.
The Technical Meaning of Joule
In the previous section, I summarized our current situation and explained the misinterpretation of the rep’s speech. This section will address the actual definition and meaning of a joule. The word joule is used in thermodynamics, chemistry, physics, and many other scientific applications. It is named after the physicist James Prescott Joule who studied the nature of heat throughout the 19th century. Represented by the letter “J” in calculation, a joule is the work completed, or energy expended, by a force moving a distance. There are three distinct ways a joule can be represented as a unit; they are mechanical work, electricity, and heat. Joule in Mechanical Work Probably the easiest way to represent a joule is in terms of mechanical work. One Joule is equivalent to one Newton moving a distance of one meter, force acting over a distance. To make this even clearer, a Newton is one kilogram (2.2 pounds) accelerated at one meter per second (3 and 1/3 feet per second). Therefore, the overall equivalent is roughly 2 pounds of material moving a distance of 3 feet and increasing its original speed by 3 feet per second. Objects can also move vertically. If an object falls from a certain height, it too has energy that can be related in terms of joules. We sense gravity all around us every second of everyday. We feel the pressure, or force, of the ground on our feet and the bed on our backs when we sleep. Therefore, since gravity is a force, it also can be converted to energy. Recall that a joule a force acting over a distance. If a ball is dropped off a tall building, the ball will have gravity forcing it downward. Joules will be expended in relation to the distance it falls. Joule in Terms of Electricity A joule is also “the work required to move an electric charge of one coulomb through an electrical potential difference of one volt” (wiki). An electric charge is an arbitrary particle with a “positive” or “negative” charge. A coulomb is the amount of positive or negative charges transported by an electric current of 1 ampere in 1 second. Basically, one particle travels through an electric field receiving a “push” from its surroundings. Joule in Terms of Heat The third use of joules is in the realm of thermodynamics and heat transfer. A joule is “the work done to produce power of one watt continuously for one second” (wiki). This is put into pretty simple terms. A watt is a unit of energy widely seen and used by most of the public.
______________________________ These definitions may not be clear enough because they are full with technical lingo and complex ideas. To make them clearer, everyday examples are included in the next section.
Real World Relations
Last section, I defined joule in three separate ways. In this section, I will use three examples to help clarify and support the definitions. There will be one example of each definition of a joule. The first example uses mechanical work; the second uses electric potential; and the third uses heat. Skateboarder A very simple example involves a skateboarder and a security guard. Let’s say the skateboarder was practicing his tricks at the skate park after it had already closed. One of the security guards working late spots the skateboarder and decides to end his night by kicking him out. Noncompliant, the skateboarder continues to perform tricks even though the security guard is yelling at the top of his lungs. Angry and frustrated, the security guard walks over to the skateboarder, grabs his shirt, and drags him to the exit. This is an example of mechanical work, which units are joules. The security guard pulling on his shirt is a force exerted. Dragging him to the entrance would be the distance he covered. As a result, it is a force exerted over a distance, the definition of a joule. Magnets Electric charge refers to the everyday expression of “positive” or “negative” charge. Now, think of a bar magnet; it has north and south poles. When opposite poles are put next to each other they are attracted. The reverse is true when similar poles are put together. They repel each other until they are far enough apart to where the effects are minimal. Magnetic forces and electrical forces work hand-in-hand. For the most part, what happens to magnets happens to electrical charges. Think of electrical charges or particles as bar magnets. If one particle (magnet 1) is still (nailed to the ground) and another similarly charged particle (magnet 2) is free to roam and placed directly next to the other, they will repel naturally. This repulsion is like a force or push. Particle 1 will move particle 2 a certain distance by pushing it with electrical force. Once again, we have force acting over a distance, the definition of a joule. Calories Every day, people look at nutrition labels on various food packages and snacks. The main thing people tend to look at is calorie intake. But what is a calorie? A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. Four Oreo cookies contain about 320 calories. If you lit your four delicious Oreos on fire and measured the energy produced, it could increase 1 gram of water 320˚C or 320 grams of water 1˚C.
In terms of heat, a joule is the exact same thing as a calorie. It is a straight conversion. One calorie equals roughly 4.1 joules. So, the 320 calories in four Oreos, one could say has 1312 joules. That 1312 joule Oreo feast could increase the temperature of 1 gram of water 320˚C. It is the amount of energy that can be expended by the Oreos, the definition of a joule.
Conclusion
A joule is a unit of energy used in many scientific applications. It measures energy performed during mechanical work, electric potential, and heat. In no way is it synonymous with the precious metals and stones we call jewels. For mechanical work, one joule is equal to a Newton acting over 1 meter. In electrical applications, a joule is the work required to move an electric charge of one coulomb through an electrical potential difference of one volt. In heat, a joule equates to the work done to produce power of one watt of energy continuously for one second. As seen in the examples, a simple, easy way to remember definition is force acting over a distance and/or energy that is expended due to motion or use. If you need me to clarify anything, call me at 555-5555 or email me at defrep1@awesomeE.com
References
"Joule." Wikipedia. 19 June 2008. 24 June 2008 . "Calorie." Wikipedia. 5 June 2008. 24 June 2008 .