help please

derek13 · Feb 1, 2009

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!!!!!

Andy™ · Feb 1, 2009

depends if 2KW is input or output....

assuming its 2KW input

it wastes 10%, so 10% of 2KW is 0.2KW

its on for 5 hours so 0.2x5 = 1KWH

springcrocus · Feb 1, 2009

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!

derek13 · Feb 2, 2009

thanks guys

Apache · Feb 2, 2009

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?

SPECIAL LOCATION · Feb 3, 2009

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?

(Output/Input) x 100

(1650/2000)x100 = 82.5%

(Output/(efficiency/100)) = Input

(480/(69/100)) = Input

480/0.69 = 695.65watts