Chapter 10 Work and Energy Questions-04
Questions
1. What is power?
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Answer
Power is defined as the rate of doing work or the rate of transfer of energy. If an agent does a work W in time t, then power is given by:
$ \begin{aligned} & \text { Power }=\frac{\text { Work }}{\text { Time }} \\ \\ & \mathrm{P}=\mathrm{W} / \mathrm{T} \end{aligned} $
It is expressed in watt (W).
2. Define 1 watt of power.
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Answer
A body is claimed to possess power of one watt if it works at the speed of 1 joule in $1 \mathrm{~s}$.
That is,
One $\mathrm{W}=1 \mathrm{~J} / 1 \mathrm{~S}$
3. A lamp consumes $1000 J$ of electrical energy in $10 s$. What is its power?
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Answer
Power $=$ Work $/$ Time
$\mathrm{P}=\mathrm{W} / \mathrm{T}$
Time $=10 \mathrm{~s}$
Work done $=$ Energy consumed by the lamp $=1000 \mathrm{~J}$
Power $=1000 / 10=100 \mathrm{Js}^{-1}=100 \mathrm{~W}$
Hence, the power of the lamp is $100 \mathrm{~W}$
4. Define average power.
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Answer
Average power is defined as the ratio of total work done by the body to the total time taken by the body.
$ \text { Average Power }=\frac{\text { Total Work Done }}{\text { Total Time Taken }} $
