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

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SUMMARY

The discussion focuses on calculating the cost of running a steam iron that draws 5.3 A from a 114 V line over a duration of 76 minutes. The internal energy produced is calculated using the formula U = VIt, resulting in 2,755,152 J. The cost calculation involves converting this energy into kW*hr, leading to confusion regarding the final answer, which should be expressed in cents. The correct conversion and calculation yield a cost of approximately 57.4 cents for running the steam iron for the specified duration.

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  • Understanding of electrical power calculations (U = VIt)
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  • Basic arithmetic operations for unit conversion and cost determination
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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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