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9.3 Exploring work and power
Why do people prefer In the modern world we come across all sorts of work – from the large
to use lifts rather processing plant working on raw materials, to a kettle being boiled to
than stairs? prepare some tea in the morning. The rate at which work is done is
important. We talk about this rate in terms of power. Power is used not
textbooks nis edu kz
only for mechanical motion; it is also used for electricity and heating
devices and all kinds of energy transfer. For example, when department
stores are promoting powerful vacuum cleaners, audio systems and
other equipment, they suggest that more power means more work. Is
this true?
The greater the power, the
more work is done in a definite
amount of time. Thus, a kettle
with greater power will boil
water in a shorter time. And a
bulb with greater power will
glow brighter and provide
better illumination. But there
is another side – a more
powerful device consumes
more electrical energy.
INV
1. Using different electric heaters (more powerful and less powerful),
design and perform an investigation to develop an understanding of
the relationship between electric power, time and temperature. What
main assumptions do you need to make to perform this experiment?
What can you say about the work done by the heaters?
2. Using different light bulbs (again, more powerful and less powerful),
design and perform an investigation to understand the relationship
between electric power and the brightness of a light bulb. What
main assumptions do you need to make to perform this experiment?
What can you say about the work done by the electric current in the
filament of the bulb or the gas in the fluorescent tube?
ACT Discuss with your classmates which kind of transport is the most
powerful. Estimate the power of each means of transport and undertake
a comparative analysis.
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