00:01
So we're given that we have a 100 watt lamp.
00:02
We're going to run it for a week continuously.
00:05
And we're told how much energy costs from our utility.
00:09
So first of all, since our energy cost is in units of hours, we should probably figure out how many hours are in a week.
00:18
Well, we know a week is seven days.
00:20
And we know a day is 24 hours.
00:22
So each one of these seven days has 24 hours in it.
00:25
So we just multiply those two together.
00:27
Seven times 24 is 168.
00:29
So we have one week is 168 hours.
00:31
So we're going to run this lamp for 168 hours straight.
00:37
So our electric company is going to charge us 12 cents for every kilowatt of power that's consumed for an hour.
00:51
So we want the product of power and time, which just gives us energy because power is energy over time multiplied by time.
01:01
It gives us energy.
01:02
So this really is saying this is how many, it's a measure of joules really, but that's not how the power company works.
01:09
They tell us, hey, let's look at your power and multiply that by time.
01:13
So we have a hundred watt lamp, but we need kilowatts down here.
01:17
So let's go and figure that out first.
01:20
So we know one kilowatt is the same as a thousand watts.
01:23
That's what kilo means.
01:24
So this relationship is always going to hold...