301 question

[dempstar]

Morning Guys & Girls

Im alittle confused with a question on 301 download & i had a question on my 301 exam similar i could not remember the formula i have it now the question being An electric motor has a power output of 1500w. The input current is 4a & the applied voltage is 400v. The efficiency of the machine will be

A.50% B.75% C.87.5% D.93.75% & i have answers too given me d

Trying to do the calc E= Output divide by input x 100 which i have done but i

get 37500 doing 1500 divide 4 x 100 what am i doing wrong please

 

[mikey-c]

Hint: check what your input value should be in your calculation.

 

[kiwiNCFC]

Basically:

output / input x 100

So 1500 / input which is 4a X 400 (P=IxV) = 1600 so 1500/1600 = 0.9375 x 100 = 93.75%