What is the difference between Energy and Power?
Simply put, energy is what you deliver and power is the rate at which you deliver it. You store energy. You can’t store power. Why is it so important to make that distinction? The distinction is essential for efficient design. That makes it a big deal. For example, you may need short-duration high power, which would require a big battery. Digital cameras need lots of power for a short duration. In the standby mode, they need simple storage technology. In the automotive world, you could downsize an engine with the right combination of power and energy. Do engineers you’ve worked with understand the difference between power and energy? Some don’t. One of my jobs is to help them understand the difference. And it’s available technology that makes the difference. Batteries used to be all we had. Now, we have ultracapacitors. Is this a problem restricted to the U.S.? No. In fact, the U.S. has a better understanding of ultracapacitors than engineers in Europe, though the latter are leaning to
With all of the talk about energy, the term power and energy have been frequently tossed about. It seems these terms have the same meaning. However, they are different. Knowing the difference will save confusion and help you understand the story which used the terms. Energy Energy is defined as the ability to do work. This is a common and general description of energy. Another view, it takes energy to do anything. Energy is needed to move your car. Energy is needed to heat your home. Energy is needed to light the night. So on and so on.
The answer is that power measures how fast energy is used (or to be persnickety about it, it measures the rate at which work is done). The electric company, for example, charges you for the total amount of energy you use during a month, whereas the power rating on an appliance or light bulb tells you how fast that appliance or light bulb will use energy. Suppose you have a 100 watt light bulb and you leave it turned on for 10 hours. You have used 100 x 10 = 1000 watt-hours, or one kilowatt-hour, of energy. Now, if you replace it with a fluorescent bulb that is only 10 watts, you would have to leave it on for 100 hours to use up the same amount of energy. The electric company doesn’t care – if you’ve used a total of one kilowatt it doesn’t matter to them if it took you 10 hours, 100 hours, 5 minutes, or the whole month to do it. But if you know you’re going to have your light on for 5 hours a day, you will use less energy if you use one that has a lower wattage rating. For another examp
Power is the rate of doing work. It is an instantaneous quantity, measured in watts. A watt is 1 joule per second. Energy is power over a period of time. It is measured in watt-seconds, but that unit is too small for everyday use, so the unit kilowatt-hours is more commonly used. Note this is a controversial subject – not because there is any disagreement, but because some people are either lazy, uninformed or misinformed and misuse the terms. The fun is that both terms, power and energy, are used loosely in everyday non-technical speech, unlike for example (non-fig) newtons. 95C) What are volts, amps, watts, joules, etc? Term Measure Definition newton force The force which will give 1 kilogram of mass an acceleration of 1 meter /second^2 dyne force 1/10^5 newtons joule work The work done when a force of 1 newton acts through a distance of 1 meter. erg work 1/10^7 joules ampere electric current 1 ampere is a charge flow of 1 coulomb per second ampere electric current “that constant cur
