NoteARific: The Other Stuff
This is the last section in the electricity unit.
•
I have sort of a bunch of leftovers that I want to show you.
•
These are examples of questions that you may need to know how to do. Some of
them are my own, some are from old diplomas, some are just questions I’ve
spotted over the years.
•
All of them need you to bring together at least a couple of the concepts you’ve
learned up till now.
•
It’s easiest to understand these questions if we work them out as examples
together.
Example 1:
A circuit with a single 25.0
Ω
resistor runs for 5.00s. During this time 15.0C
pass through a point in the circuit.
a) What is the power rating of this circuit?
First we will figure out the current…
I = q/t = (15.0C) / (5.00s) = 3.00A
Then we can figure out the power…
P = I
2
R = (3.00A)
2
(25.0
Ω
) =
225W
b) How much energy is used?
P = W / t
W = Pt = (225W) (5.00s)
W =
1.13 x 10
3
J
c) Throw a 5.0kg box straight up into the air using the same amount of energy.
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 Fall '08
 RABE
 Physics, Resistor, 5%, 23 m, 60w, 57w

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