Teaching around the nature of power is supported by 8 key concepts:

1.1 power is a amount that is moved from mechanism to system. Power is the capacity of a mechanism to do work. A system has done work-related if it has exerted a pressure on an additional system over some distance. As soon as this happens, power is transferred from one system to another. At the very least some of the energy is likewise transformed from one type into an additional during this process. One can keep track of just how much power transfers right into or the end of a system.

You are watching: Power is the rate at which energy is transformed


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What form of energy is pictured here?The Thunder Dolphin rollercoaster in Tokyo Japan reaches speeds of 81 mph. Photograph by Ben Garney.
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Misconceptions are typical when it involves understanding develops of energy. Top top one hand, us all have actually an intuitive sense of what energy is. But the scientific research behind energy can be complex. Teachers need to find a center ground in between offering accurate explanations, while not oversimplifying or developing further misconceptions.

A common stumbling block is the principle of power and also the systems to describe energy and also power. In the metric system, the devices use to measure energy are Joules. A Joule is the lot of energy required to accelerate a 1 kg object to a rate of 2 m/s, or to lift a 1 kg object around 10 centimeter vertically. Calories, BTUs, and kilowatt hrs are other units that deserve to be used to measure up energy.

Power, which is the price of energy transfer, is measure in Joules every second, also called Watts. Unlike other units that define rates (for example, miles per hour for speed, dollars every hour because that wages) the unit "Watt" has actually the "per second" already built in to the unit. Without the acquainted "per second" in the units, students often think the a Watt is a quantity of energy, quite than a rate at which energy is transferred. For example, a 100 Watt light bulb uses 100 Joules of electrical energy every second, transforming that mostly into thermal energy.

Adding come this confusion is the unit kilowatt hour. A kilowatt hour is 1000 watt times 3600 seconds, or 3.6 million Joules. This is a common unit of power for electrical utilities come use when billing,

A comparable and amusing example of the confusion approximately power and also energy is that electric utilities room often called "power" companies, also though the product they market is energy.

Bringing these principles into your classroom


As is depicted in the TED-ed video, basic mathematical ideas can be supplied to know how energy is quantified, such together measuring energy from two different forms, climate converting those amounts into common units. Terms together as power (energy end time), work (force end distance) deserve to be quickly measured and calculated. Every one of these terms have actually alternate, but related, interpretations in everyday life, so acquiring students familiar with the mathematical definitions will call for students to know slightly different interpretations for the very same words.

Many creates of energy change are directly observable in the classroom, so demonstrations space an effective way to illustrate transformations in between different creates of energy.

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Show instances of great demonstrations portraying different develops of energy
A chemistry battery running a irradiate bulb the illuminates a surface: chemical energy is revolutionized into electrical energy, i m sorry is revolutionized to radiant and also (mostly) heat energy. Evaluating the labeling top top a light bulb enables students to calculate the effectiveness by detect the ratio of light output (lumens) come power provided (Watts). Higher efficiency light bulbs will produce more lumens of visible light per Watt.

Hand-crank generator/motors and a light bulb display how kinetic energy can be changed into electric energy. Connecting 2 handheld generator/motors together shows exactly how kinetic deserve to be revolutionized to electric and also then earlier to kinetic. A Peltier junction (or thermo electric generator) transforms electrical energy into a temperature difference, or a temperature distinction into electrical energy. So-called "happy/sad" balls easily accessible from science education and learning supply companies present how the elasticity that a material can influence energy transfer. The "happy" sphere is do of a polymer that, when compressed, shop elastic potential energy and releases a comparable amount the kinetic energy when that is uncompressed. Because that example, when the ball is dropped indigenous a height of 1 meter, the gravitational potential power is convert to kinetic power as the ball falls. Once the ball impacts the floor, the round compresses and also the kinetic power is converted into mostly elastic potential energy (and some thermal energy). When the ball re-bounds, the elastic potential is converted ago to greatly kinetic power (again, part thermal) bring about the sphere to re-bound come a far-ranging fraction the the elevation from which the is released. The ratio of the re-bound height to the release elevation is the ratio of final energy of the system to the original power -- an calculation of the energy transfer efficiency. The "sad" sphere is make of a polymer that is less elastic. Once this round is compressed, almost all of the mechanical energy is converted to heat energy and the sphere does not re-bound noticeably. Spring toys and also poppers are other examples of comparable energy transformations. A dewar or vacuum flask "thermos" is great example of deliver of thermal energy. Describing exactly how a vacuum flask keeps thermal power from being moved either in or out helps college student realize the "coldness" is not a quantity, or a type of energy, yet rather a absence of heat energy. Students might be interested in the story the the breakthrough of the vacuum flask and also how it to be commercialized through Thermos that benefited from the fact that Dewar did not patent the idea.

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References

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

PhET simulations for to teach Energy, Work and Power. Interaction simulations that allow students to "experiment" with transforming variables in various energy systems.

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The Physics class is one online, free-to-use physics website developed primarily for high institution physics students and also teachers. For example, the animation of power Transformations for Downhill Skiing illustrates the relationship between work and also energy.