Annual cost to operate a 100w and 25w light bulb.

Question

amtran_bus · Answer

attachment

anonymous · Answer

Seems like physics! :/

e.mccormick · Answer

And what problem are you having with this?

amtran_bus · Answer

Thankfully not.

amtran_bus · Answer

I need help with the conversions.

e.mccormick · Answer

What conversions?  They are all in the same units.

amtran_bus · Answer

This problem

e.mccormick · Answer

OK... well... kW vs W.  k = 1000.

e.mccormick · Answer

Other than that, I do not see conversions.  I just see simple math with variables.

amtran_bus · Answer

I need help with it all.

e.mccormick · Answer

OK.  So, did you start by getting the numbers and formula out of the question?  That is the best thing to do first in any word problem.

ybarrap · Answer

The units of watts is Joules/sec. We need to see how many Joules (i.e. units of energy) are consumed in one year for 100 Watts and 25 Watts.

Start with 100 Watts. Find out how much energy is consumed in one year:

100 Watts = 100 Joules/sec * Number of Seconds in Y year = $\Large E_{100w}$

We know that charge for energy is $.19/ kw h. 

Let a=1 kw h = 1000 J/s * 3600 sec

So charge per kw h is $0.19/a, which gives units of $ per Joule.

Once you get this, multiply times $\Large E_{100w}$ to get your answer.

Repeat for the 25W bulb.

ybarrap · Answer

Let me know if you have any questions.

amtran_bus · Answer

Got it right thanks