Calculating Energy Usage of a Hair Dryer

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To calculate the energy usage of a 1650-W hair dryer in 10 minutes, the correct approach involves converting the time to seconds, leading to a total of 9.9 x 10^5 Joules. For part (b), the total usage over 4.5 hours needs to be calculated in kilowatt-hours to determine the cost at a rate of 12 cents per kWh. The user initially struggled with unit conversions and applying the power formula correctly. After receiving guidance, they successfully solved part (a) and are now focused on completing part (b). Accurate unit conversions are essential for solving energy-related calculations effectively.
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[SOLVED] Power problem!

Homework Statement



(a) How many joules of electrical energy are used by a 1650-W hair dryer in 10 min? (b) If the dryer is operated a total of 4.5 h during one month, how much will this contribute to the electrical bill if the billing rate is 12 cents/kWh?

Homework Equations



P=\frac{w}{t} --> w=Pt

The Attempt at a Solution



(a) w=Pt -> (1650)(10)= 16500 J

I figured since the answer was supposed to be in Joules, I would use the equation w=Pt to figure out the amount but I ended up getting the wrong answer. The correct answer is 9.9 x 10^{5}.

(b) Since I didn't get the right answer for (a) I knew my answer wouldn't be right here either. I don't really know how to solve this question either but I figured I should convert the 4.5 h into minutes so it matches the amount for part (a)..so I got 190 minutes, and that's pretty much it.

Please help, we didn't get any notes to refer to for this homework and it is our first day learning about Power. :confused:
Thanks so much.:smile:
 
Last edited:
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(a) w=Pt -> (1650)(10)= 16500 J

For part (a): since 1 Watt = 1 Joule/second, you need to change the 10 minutes into seconds to keep your units consistent.
 
ok thanks...i got part a! now I am just workin on b...
 

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