Finding Joules of heat for 75% efficient motor at 250hp.

In summary, the problem is to find the Joules of heat per hour produced in a motor that is 75% efficient and requires 0.250hp to run it. The efficiency equation is 1-(Qc/Qh). The attempt at a solution involved converting hp to Watts, multiplying by 75% to get 139W, but the book gives the answer as 168kJ. After trying for hours, the problem was still unsolved.
  • #1
Moose100
116
0

Homework Statement


Forgive me for any indiscretions my first post.

The problem is to find the Joules of heat per hour produced in a motor that is 75% efficient and requires 0.250hp to run it.

Homework Equations



efficiency=1-(Qc/Qh)

The Attempt at a Solution



1. convert hp to Watts; 0.250hp* 746W/hp *75 percent=139W

At this point the answer is wrong and I don't know why. I have tried for hours to solve this please help!
 
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  • #2
Try multiplying by 25 percent instead. 75% efficient means that 25% of the applied work is converted to heat.
 
  • #3
I did the problem is that gives me a small number at around 48 the bok says the answer is 168KJ


It's 139 when I multiply by 75%
 
  • #4
I don't know then. Would you mind typing out the problem exactly as it is stated?
 
  • #5
No problem.

How many joules of heat per hour are produced in a motor that is 75.0 percent efficient and requires 0.250hp to run it? Ans 168kJ
 

FAQ: Finding Joules of heat for 75% efficient motor at 250hp.

How is efficiency calculated for a motor?

The efficiency of a motor is calculated by dividing the output power by the input power and multiplying by 100%. In this case, the output power would be 250 horsepower and the input power would be the amount of electricity used to power the motor.

What is the formula for calculating joules of heat?

The formula for calculating joules of heat is Q = MCΔT, where Q is the amount of heat energy, M is the mass of the substance, C is the specific heat capacity of the substance, and ΔT is the change in temperature.

How do you determine the efficiency of a motor?

The efficiency of a motor can be determined by comparing the input power (electricity used to power the motor) to the output power (mechanical work produced by the motor). The efficiency is usually expressed as a percentage and can be calculated by dividing the output power by the input power and multiplying by 100%.

What is the significance of finding joules of heat for a motor?

Finding joules of heat for a motor is important because it allows us to understand the amount of energy lost as heat during the motor's operation. This information can be used to improve the efficiency of the motor and reduce energy waste.

How does the efficiency of a motor affect its performance?

The efficiency of a motor directly impacts its performance, as a more efficient motor will require less energy to produce the same amount of mechanical work. This can result in cost savings and a longer lifespan for the motor.

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