Calculating Daily Operating Cost for a Motor at Rated Load

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Homework Help Overview

The problem involves calculating the daily operating cost of a motor that operates at a rated load of 10 horsepower for 8 hours a day, with an efficiency of 87 percent and an electric energy cost of 5 cents per kilowatt-hour.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the conversion of horsepower to watts and the importance of factoring in both the operating time and the motor's efficiency in the cost calculation. Questions arise regarding the appropriate formula to use and the need for a more detailed attempt at the solution.

Discussion Status

The discussion is ongoing, with some participants providing guidance on the need to consider efficiency and operating time in the calculations. There is a call for more detailed attempts at solutions from the original poster and others, indicating a collaborative effort to clarify the problem.

Contextual Notes

Participants note that the original poster's calculation did not include the impact of efficiency on the power input required for the motor's operation, which is a critical aspect of the problem.

holy_kamote
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Homework Statement


a motor operates at its rated load of 10 hp for 8.0 h a day. its efficiency is 87 percent. what is the daily cost of operation if electric energy costs 5 cents/kWh?



Homework Equations





The Attempt at a Solution


i convert 10 hp to watts
10 x 746=7460 watts
then i multiply the 7460 with 5 cents and i get 37.3cents/daily cost...
is my answer correct? if not plsss post some idea on how i can solve that ty very much...
 
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help me plsssss. coz we will have a boardwork tomorrow ..
 
You are missing a couple of things. The motor is operating for 8 hours each day...you didn't factor that in. Also, you didn't factor in the efficiency rating. If the motor is rated at 10 hp , that's how much power you get out of it...but more power has to go into it due to the inefficiency losses within the motor, and that's what you pay for.
 
what formula will i use to solve this prob?... thanks sir jay for posting in my topic.
 
Please show an attempt at a solution. If the motor is 87% efficient, the power into the motor is greater than 10 hp. First calculate that number. Then once you get that power, how would you convert it to energy used (kWh) in 8 hours? We can't be of much more help unless you show some attempt. Thanks.
 

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