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Calculating Efficiency.


Efficiency (%) = Useful Energy Out x 100
Total Energy In

Questions

1) A light bulb takes in 30J of energy per second. It transfers 3J as
useful light energy and 27J as heat energy. Calculate the efficiency.
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2) A kettle takes in 2000J of energy…

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2) Convert the following powers into kilowatts
a) 3000W _________________________________
b) 20W ___________________________________
c) 900W __________________________________
d) 20000W ________________________________
e) 1W ____________________________________

energy transferred = power x time
(kilowatthour, kWh) (kilowatt, kW) (hour, h)


Remember: When calculating energy transferred; power
MUST be in kW and time MUST be…

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8) Julie uses her hair dryer for 30 minutes. The hair dryer has a
power of 500W. Calculate the cost of Julie drying her hair if each
kWh costs 8p.
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In the exam you will be given the formulas for the
calculations you will have to do.…

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Radiation

1) Radiation can travel through a vacuum; what is a vacuum?
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2) What kind of surface emits the most thermal radiation?
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3) What kind of surface reflects the most thermal radiation?
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4) What kind of surface absorbs the most thermal radiation?
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Payback Time





1) Fill…

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Generating Electricity

A renewable energy source is one which will not run out and is
continually being replaced
A nonrenewable energy source is one which will run out and cannot be
replaced


1) Give three examples of fossil fuels?
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2) Which non-renewable energy source does not contribute to the…

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