## Teaching about the nature of power is supported by 8 vital concepts:

1.1 energy is a amount that is transferred from system to system. Power is the capacity of a system to do work. A system has done work-related if it has actually exerted a force on an additional system over part distance. When this happens, power is moved from one system to another. At least some that the power is additionally transformed native one form into an additional during this process. One deserve to keep track of how much power transfers into or the end of a system.

You are watching: Rate at which electric energy is converted to another form What form of energy is pictured here?The Thunder Dolphin rollercoaster in Tokyo Japan reaches speed of 81 mph. Picture by Ben Garney.  Misconceptions are usual when it concerns understanding forms of energy. Top top one hand, us all have an intuitive sense of what energy is. But the scientific research behind energy can be complex. Teachers require to find a middle ground in between offering exact explanations, while not oversimplifying or producing further misconceptions.

A common stumbling block is the principle of power and also the systems to define energy and also power. In the metric system, the systems use to measure power are Joules. A Joule is the quantity of power required to advice a 1 kg object to a rate of 2 m/s, or to lift a 1 kg object around 10 cm vertically. Calories, BTUs, and kilowatt hrs are other units that have the right to be used to measure energy.

Power, which is the price of energy transfer, is measured in Joules per second, likewise called Watts. Unlike various other units that describe rates (for example, miles per hour because that speed, dollars per hour because that wages) the unit "Watt" has actually the "per second" already built in to the unit. There is no the acquainted "per second" in the units, students regularly think the a Watt is a quantity the energy, rather than a rate in ~ which energy is transferred. Because that example, a 100 Watt irradiate bulb supplies 100 Joules of electrical energy per second, transforming it mostly into thermal energy.

Adding to this confusion is the unit kilowatt hour. A kilowatt hour is 1000 watts times 3600 seconds, or 3.6 million Joules. This is a typical unit of power for electric utilities to use when billing,

A similar and amusing example of the confusion approximately power and also energy is that electrical utilities room often dubbed "power" companies, even though the product they sell is energy.

## Bringing these principles into her classroom

As is depicted in the TED-ed video, an easy mathematical ideas can be used to recognize how power is quantified, such as measuring energy from two different forms, climate converting those quantities into usual units. Terms together as strength (energy end time), work (force over distance) deserve to be conveniently measured and also calculated. Every one of these terms have alternate, yet related, meanings in everyday life, so getting students acquainted with the mathematical interpretations will require students to know slightly different interpretations for the exact same words.

Many develops of energy change are directly observable in the classroom, so demonstrations are an effective method to illustrate transformations between different creates of energy. Show examples of great demonstrations showing different develops of energy
A chemistry battery running a light bulb that illuminates a surface: chemical energy is reinvented into electrical energy, which is revolutionized to radiant and also (mostly) heat energy. Assessing the labeling top top a light bulb permits students to calculation the efficiency by detect the ratio of light calculation (lumens) come power supplied (Watts). Higher efficiency irradiate bulbs will produce more lumens of clearly shows light every Watt.

Hand-crank generator/motors and a irradiate bulb display how kinetic energy can be revolutionized into electrical energy. Connecting two handheld generator/motors with each other shows exactly how kinetic have the right to be reinvented to electric and also then back to kinetic. A Peltier junction (or thermo electric generator) transforms electrical energy right into a temperature difference, or a temperature difference into electrical energy. So-called "happy/sad" balls easily accessible from science education and learning supply companies display how the elasticity that a material can impact energy transfer. The "happy" round is do of a polymer that, as soon as compressed, shop elastic potential energy and releases a comparable amount the kinetic power when the is uncompressed. Because that example, once the ball is dropped indigenous a elevation of 1 meter, the gravitational potential energy is converted to kinetic power as the sphere falls. When the ball impacts the floor, the sphere compresses and also the kinetic energy is converted into mostly elastic potential power (and part thermal energy). When the sphere re-bounds, the elastic potential is converted earlier to mostly kinetic energy (again, some thermal) causing the ball to re-bound come a significant fraction of the height from which that is released. The proportion of the re-bound elevation to the release elevation is the proportion of final power of the system to the original energy -- an calculation of the power transfer efficiency. The "sad" round is made of a polymer the is less elastic. When this round is compressed, almost every one of the mechanical energy is convert to heat energy and the ball does no re-bound noticeably. Spring toys and poppers space other instances of comparable energy transformations. A dewar or vacuum flask "thermos" is fantastic example of transfer of heat energy. Describing how a vacuum flask keeps thermal energy from being moved either in or out helps student realize that "coldness" is not a quantity, or a kind of energy, however rather a absence of thermal energy. Students might be interested in the story of the development of the vacuum flask and how it to be commercialized by Thermos that benefited native the reality that Dewar did not patent the idea.

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## References

What is Energy? indigenous EIA energy Kids, this unit covers power basics, species of energy, power units and energy calculators.

PhET simulations for teaching Energy, Work and also Power. Interactive simulations that permit students come "experiment" with transforming variables in different energy systems.

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The Physics great is one online, free-to-use physics website occurred primarily because that high college physics students and teachers. Because that example, the animation of power Transformations for Downhill Skiing illustrates the relationship in between work and also energy.