13.3 电力
Section outline
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Did you ever sweep a floor with a broom, like the woman in the picture on the left? It can take a lot of effort to do the job. But if you use an electric vacuum cleaner, like the woman in the picture on the right, you can do the same work more easily and quickly. That’s because the vacuum cleaner provides more power.
::你曾经用扫帚扫过地板吗? 就像左边照片中的女人那样? 这项工作需要很多努力才能完成。 但如果你使用电吸尘器,像右边照片中的女人那样,你可以更容易和迅速地做同样的工作。 这是因为真空吸尘器提供了更多的动力。What Is Power?
::什么是权力?Power is a measure of the amount of work that can be done in a given amount of time. Power can be represented by the equation:
::权力是衡量在一定时间内能够完成的工作量的尺度。
::Power=工作时间In this equation, work is measured in joules (J) and time is measured in seconds (s), so power is expressed in joules per second (J/s). This is the SI unit for power, also known as the watt (W) . A watt equals 1 joule of work per second. You’re probably already familiar with watts. Light bulbs and small appliances such as microwave ovens are labeled with the watts of power they provide. For example, the package of light bulbs in the Figure is labeled “14 watts.”
::在这个方程中,工作用焦耳(J)衡量,时间用秒(s)衡量,因此电量以焦耳/秒(J/s)表示。这是SI的功率单位,也称为瓦特(W)。一瓦特等于每秒工作1焦耳。你可能已经熟悉瓦特。灯泡和微波炉等小型器械被贴上它们所提供的功率瓦特的标签。例如,图中的灯泡包被贴上“14瓦特”标签。Q : Assume you have two light bulbs of the same type, such as two compact fluorescent light bulbs like the one pictured in the Figure . If one light bulb is a 25-watt bulb and the other is a 60-watt bulb, which bulb produces brighter light?
::问题:假设你有两个同类的灯泡,例如两个紧凑的荧光灯泡,如图中图中的灯泡。如果一个灯泡是25瓦的灯泡,另一个灯泡是60瓦的灯泡,哪个灯泡产生更亮的灯光?A : The 60-watt bulb is more powerful, so it produces brighter light.
::答:60瓦灯泡更强大,Compared with a less powerful device, a more powerful device can either do more work in the same time or do the same work in less time. For example, compared with a low-power microwave oven, a high-power microwave oven can cook more food in the same time or the same amount of food in less time.
::与功率较低的设备相比,更强大的设备既可以在同时做更多的工作,也可以在较短的时间做同样的工作。 比如,与低功率微波炉相比,高功率微波炉可以在同时做更多的食物,或者在更少的时间里做同样数量的食物。Calculating Power from Work and Time
::计算工作与时间的电源Power can be calculated using the formula above if the amount of work and time are known. For example, assume that a microwave oven does 24,000 joules of work in 30 seconds. Then the power of the microwave is:
::如果已知工作量和时间,可以使用以上公式计算功率。例如,假设微波炉在30秒内完成24 000焦耳的工作。然后微波的功率是:
::Power=WorkTime=24000 J30s=800 J/s,或800 WQ : Another microwave oven does 5,000 joules of work in 5 seconds. What is its power?
::问题:另一个微波炉在5秒内完成5 000焦耳的工作。它的功率是什么?A : The power of the other microwave oven is:
::A:另一个微波炉的功率是:
::Power=5000 J5s=1000 J/s, 或1000 WQ : Which microwave oven will the same amount of food in less time?
::问:在较短的时间内,哪个微波炉能提供同样数量的食物?A : The 1000-watt microwave oven has more power, so it will heat the same amount of food in less time.
::A:1000瓦微波炉的电量更大,Calculating Work from Power and Time
::从时间和动力计算工作You can also calculate work if you know power and time by rewriting the power equation above as:
::如果您知道功率和时间,您也可以将上面的功率方程式重写为:Work = Power × Time
::工作=动力x时间For example, if you use a 1000-watt microwave oven for 20 seconds, how much work does it do? First express 1000 watts in J/s and then substitute this value for power the work equation:
::例如,如果使用千瓦微波炉20秒,它能工作多少?首先在 J/s 中显示1000瓦,然后用这个值来驱动工作方程式:Work = 1000 J/s × 20 s = 20,000 J
::工作=1000 J/s × 20 s = 20,000 JHorsepower
::马力Sometimes power is measured in a unit called the horsepower. For example, the power of car engines is usually expressed in horsepowers. One horsepower is the amount of work a horse can do in 1 minute. It equals 746 watts of power. Compare the horsepowers in the Figure to the other Figure .
::有时用一个称为马力的单位来测量功率。例如,汽车发动机的功率通常以马力表示。一匹马力是马能在一分钟内完成的工作量,等于746瓦的功率。将图中的马力与其他图中的马力相比较。This team of three horses provides 3 horsepowers of power. This big tractor provides 180 horsepowers of power. Q : If the team of three horses in the Figure and the tractor in the Figure do the same amount of work plowing a field, which will get the job done faster?
::问:如果图中的三匹马和图中的拖拉机队在田地上做同样多的耕种工作,这样就能更快地完成工作?A : The tractor will get the job done faster because it has more power. In fact, because the tractor has 60 times the power of the three-horse team, ideally it can do the same work 60 times faster!
::甲:拖拉机能够更快地完成任务,因为它的功率更大。事实上,因为拖拉机拥有三匹马队的60倍的功率,最好它能更快地完成同样的工作60倍!Summary
::摘要-
Power is a measure of the amount of work that can be done in a given amount of time. Power equals work (J) divided by time (s).
::权力是衡量在一定时间内能够完成的工作量的尺度,权力等于工作(J)除以时间。 -
The SI unit for power is the watt (W), which equals 1 joule of work per second (J/s).
::SI电力单位是瓦特(W),等于每秒工作1焦(J/s)。 -
Power can be calculated from work and time using the equation:
::电能可使用公式:Power=WorkTime(Power=WorkTime)根据工作和时间计算电能。 -
Power may be measured in a unit called the horsepower. One horsepower is the amount of work a horse can do in 1 minute, which equals 746 watts of power.
::一种马力是马在1分钟内能完成的工作量,等于746瓦的功率。
Review
::回顾-
What is power? What is the SI unit for power?
::什么是力量? -
How much power does a toaster have if it does 1,000 joules of work in 30 seconds?
::如果烤面包机在30秒内 完成1000焦耳的工作,它能有多少动力? -
How much work can be done in 30 seconds by a 1000-watt microwave oven?
::一个1000瓦微波炉在30秒内能完成多少工作? -
Lamar’s mom has a car with a 182-horsepower engine. How many watts of power is that?
::拉马尔的母亲有一辆有182马力引擎的汽车。 有多少瓦的电能?
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Power is a measure of the amount of work that can be done in a given amount of time. Power equals work (J) divided by time (s).