How Do You Calculate the Cost of Running a Steam Iron?

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Homework Help Overview

The problem involves calculating the internal energy produced by a steam iron and determining the cost of running it over a specified duration. The subject area includes electrical energy calculations and cost analysis based on power consumption.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the calculation of internal energy using the formula U = VIt and explore the conversion of energy from joules to kilowatt-hours for cost estimation. There are questions regarding the accuracy of the cost calculation and the correct unit conversion process.

Discussion Status

Some participants have provided guidance on unit conversions and reiterated the need to express the final answer in cents. There appears to be confusion regarding the correct interpretation of the cost calculation, as multiple participants report similar results but indicate they are marked incorrect.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may impose specific formatting or unit requirements for the answers. There is an ongoing discussion about potential misinterpretations of the cost calculation.

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Homework Statement


A steam iron draws 5.3 A from a 114 V line. (a) How much internal energy is produced in 76 minutes? Answer in J. (b) How much does it cost at $0.75/kW*hr to run the steam iron for 76 minutes? Answer in units of cents.


Homework Equations


1) U = VIt


The Attempt at a Solution


Using equation 1, I found the internal energy produced to be 2755152 J. However, I'm having a problem with figuring out part (b). I know I'm supposed to convert J to kW*hr in order to figure out the cost and that 1 watt = 1 J/s. Using that information I divided the internal energy by the time, 4560 seconds, giving me 604.2 watts or 0.6042 kW. I then times that by the cost per kW/hr and the amount of time in hours. I got 0.57399, but for some reason it's not the right answer.
 
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2755152 J =2755152 Ws

Divide by 1000 to get it in kWs, then divide by 3600s to get it in kW*hr
 
peaceandlove said:
Answer in units of cents.
... I got 0.57399, but for some reason it's not the right answer.

Maybe enter it in cents?
 
rock.freak667 said:
2755152 J =2755152 Ws

Divide by 1000 to get it in kWs, then divide by 3600s to get it in kW*hr

I tried that and I get the same exact answer that I got. I even tried putting it in as 0.57 but that was marked wrong as well...
 
peaceandlove said:
I tried that and I get the same exact answer that I got. I even tried putting it in as 0.57 but that was marked wrong as well...

Your answer is $0.57399, convert that into cents.
 

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