motor efficiency

[searley]

can any body help ?

1. if a motor with the efficiency of 60% has an input of 12kw the output power will be ?

2. a 3kw wall mounted bathroom heater has an efficiency of 85%.how much power is lost over 2 hours of use ?

can anybody show me how to work these out before i kill my collage lecturer.

the answers.

1 is 7.2kw

2 is 0.9 kwh

 

[Andy™]

1: very easy, 12x 0.6 = 7.2KW

2: slightly harder.....

KWH x Hrs =6KWH

you need to find 15% of that, so 6x 0.15 give you 0.9KWH

There are other ways, like /100 x % (i.e /100 x 15) which would also get you your answer