Lecture­Power.notebook
January 15, 2013
Which car wins in a drag race?
Why?
Lecture­Power.notebook
January 15, 2013
Which car wins in a drag race?
Why?
POWER!!!
Power = work done per time interval
P=W
t
Lecture­Power.notebook
January 15, 2013
Let's expand the formula to find the UNITS:
W
P =
t
Lecture­Power.notebook
January 15, 2013
Let's expand the formula to find the UNITS:
F*d
W
P =
t = t
Lecture­Power.notebook
January 15, 2013
Let's expand the formula to find the UNITS:
F*d
W
ma*d
P =
t = t = t
Lecture­Power.notebook
January 15, 2013
Let's expand the formula to find the UNITS:
F*d
W
ma*d
P =
t = t = t
m / 2)(m)
2
kg(
kg*m
s
Power is measured in:
=
s
s3
(I told you this was going to get ugly!!!)
Lecture­Power.notebook
January 15, 2013
What do we call that mess?
Lecture­Power.notebook
January 15, 2013
What do we call that mess?
We call that mess the Watt.
Lecture­Power.notebook
January 15, 2013
The what?
Lecture­Power.notebook
January 15, 2013
NO!!!
THE
WATT!!!
Lecture­Power.notebook
January 15, 2013
DEMO TIME:
...wait...
...what!?
100g
Here is just one of
many mays we can see
what
happens when a
Watt
happens:
100g
Lecture­Power.notebook
January 15, 2013
What is the difference, and why?
60 W
100 W
Lecture­Power.notebook
January 15, 2013
What is the difference, and why?
60 W
The 100 W bulb does more WORK every second.
For the 100W Bulb:
Every second, 100 J of electrical P.E. is turned into heat and LIGHT!!! For the 60W Bulb:
Every second, 60 J of electrical P.E. is turned into heat and LIGHT!!! 100 W
Lecture­Power.notebook
January 15, 2013
P = W / t (Joules / second)
Work equals Power * Time
W = P t
From the power company, you buy Kilo­Watt Hours
That's Power * Time.
Work = Change in Energy
Lecture­Power.notebook
1 watt­hour is equivalent to:
1 Watt * 1 Hour
1 Watt = 1 Joule / 1 Second
How many Joules of energy in 1 Watt Hour?
January 15, 2013
Lecture­Power.notebook
January 15, 2013
1 watt­hour is equivalent to:
1 Watt * 1 Hour
1 Watt = 1 Joule / 1 Second
How many Joules of energy in 1 Watt Hour?
1 J*hour
sec
3600 sec
hour
X = 1 Watt Hour = 3,600 joules
Lecture­Power.notebook
1 Watt Hour = 3,600 joules
Thus a Kilowatt Hour is: 1000 X 1 Watt Hour =
1000 X 3,600 Joules =
3,600,000 joules = 1 kWh
or 3.6 megajoules. = 1 kWh
Currently we pay less than 14 cents for a Kilowatt Hour!!!
January 15, 2013
Lecture­Power.notebook
Bureau of Labor Staistics
January 15, 2013
Lecture­Power.notebook
January 15, 2013
DEMO TIME!!!
Could you light a lightbulb?
Lecture­Power.notebook
January 15, 2013
DEMO TIME!!!
Check this out:
Lecture­Power.notebook
Toys, Toys, TOYS!!!
...SHOW US MORE TOYS!!!
January 15, 2013
Lecture­Power.notebook
He­Man saiz
its time for:
WB 8­1
January 15, 2013