help please

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derek13

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just doing some revision and gone brain dead ???

a 2 kw heater is 90% efficent and is switched on for 5 hours . what is the energy wasted?????

anybody help on this please with right formula and workin out would appreciate it cheers!!!!!

 
90% efficient so 10% wasted. For 5 hours

2000 * 10 *5 / 100 = 1000

Heater wastes 0.2kW per hour, five hours = 1kW

Must type faster - Andy beat me by miles!

 
ooh here's a little test

A heater has a input of 2Kw and an outout of 1650 watts - what's it's efficiency?

A heater has an output of 480W and an efficiney of 69% - what is it's input?

 
ooh here's a little testA heater has a input of 2Kw and an outout of 1650 watts - what's it's efficiency?

A heater has an output of 480W and an efficiney of 69% - what is it's input?
can I try? :D

(Output/Input) x 100

(1650/2000)x100 = 82.5%

(Output/(efficiency/100)) = Input

(480/(69/100)) = Input

480/0.69 = 695.65watts

:) :D

 
i was tempted to 'answer' your quiz with the wrong answers - just to see if you noticed they were wrong...
too late now. I never actually checkd SL with a calculator but they agree with my mental ball park figure!

:)

 
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