Power
Power
Power :Power can be defined as the amount of work done per unit time.
Some examples :
1. You may have noticed that old people find it difficult to climb a flight of stairs quickly. But they can easily climb the same flight of stairs slowly. In both cases they spend the same amount of their stored energy and do the same amount of work in climbing the stairs. But the rate at which energy is spent or work is done is different in the cases.
2. Let us take another example. You can keep your hands immersed in lukewarm water for hours. But you cannot keep them in boiling water the cases. However, the rate at which energy is transferred is different in the two cases. As a result, they have different effects.
We see that in many cases the rate at which work is done or energy is transferred is an important quantity. Hence, this quantity is given a separate name - power. The rate at which work is done by a force is called the power delivered by that force.` Also, the rate at which energy is transferred by an object (like a machine) is called the power delivered by that object.
Definition :
The time rate of doing work is defined as power(P) . If equal works are done in different times, power will be different. More quickly work is done, power will be more.
As work W is measured in joules and time t in seconds, the unit of power is joule/second. This unit is given a separate name - watt. If work is done at the rate of 1 joule per second, the power P delivered is 1 watt (1 watt = 1 joule/second). The symbol of watt is W. Kilowatt (kW) and megawatt (MW) are also commonly used units of power.
Another common unit of power is the horse power. Horse power is written in short as hp. Horse power is related to watt as
1 horse power = 746 watt
A man carrying a bag of mass 25 kg climbs up to a height of 10 m in 50 seconds. Calculate the power delivered by him to the bag. | |||
| Right Option : A | |||
| View Explanation | |||
1 unit of electricity consumed is same as | |||
| Right Option : A | |||
| View Explanation | |||
A boy of mass 55 kg, runs up a flight of 40 stairs, each measuring 0.15 m in 5s. Column II given numerical value for quantities describe in column I, Choose the correct option
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| Right Option : A | |||||||||||||
| View Explanation | |||||||||||||
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