Motor question

[lloyd B]

An old .05hp motor 120v 80% efficient is being replaced with a .05hp 120v 90% efficient what percent of efficiency will the new motor be over the old.

 

[infinity]

What answer did you get?

 

[cosmos]

12.5% increase?

 

[lloyd B]

What formula did you use to come up with that.I had figured 11%.

 

[infinity]

I had 11.3%.

 

[cosmos]

I give up -what's the correct answer

I give up -what's the correct answer

My guess was: 90%-80%= 10% divided by 80% = 12.5% increase

 

[1793]

My guess was: 90%-80%= 10% divided by 80% = 12.5% increase

My take is: 90%-80%= 10% divided by 90% = 11.11% increase

 

[jtester]

My take is: 90%-80%= 10% divided by 90% = 11.11% increase

Since the question mentions increase over the old efficiency, I think you'd use .8 in the denominator, not .9.

Jim T

 

[1793]

Since the question mentions increase over the old efficiency, I think you'd use .8 in the denominator, not .9.

Jim T

Your right my bad. Thanks for catching my mistake.

 

[Ken9876]

You didn't happen to take and see this on an experior test did you?

 

[POWER_PIG]

so what is it?

so what is it?

Could somebody please explain this calcuation?
If your new motor is 90% eff over the old 80% why wouldnt the difference just be 10%....where can I find an example of the mechanics behind this calcualtion?