DC Stuff Continues. W7D3. This Week + peek into the future. Quiz on DC Circuits Complete Unit #8 Be sure to download the next unit from the website. Best Guess about Exam #2 Monday, October 18 th Yes, that’s in about one week! Review session on Monday morning @ 7:30AM
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DC Stuff Continues
W7D3
E= enf=internal voltage
Internal resistance reduces
the effective voltage of the
battery.
E
Use this in the experiment with the W wire!
What goes in must come out!
I
Direction doesn’t matter.
If you start at a point in a circuit and go around the loop and return to the same place, the change in potential is zero. Or: The sum of the voltage rises = the sum of the voltage drops=0
I
Overview dc circuit preliminariesw7d1
October 4, 2010
I
L

+
A
V
(Average) Current Density
The total charge moving from A to B must be the
Same or charge would build up at the interface.
I
A B
I
L

+
A
V
A wire has a resistance of 20 Ω. It is melted down, and from the same volume of metal a new wire is made that is three times longer than the original wire. What is the resistance of the new wire?
The Real Deal
A current I flows through a device. The difference in potential
from one side of the device to the other is V. How much POWER
is dissipated in the device?
DC CircuitsW7D2
Instructor BindellCourse 2054 Fall 2010
DC Circuits III
W8D1
Noooo!! –
Not another one!!
Problem Review as usual at 7:30 AM
Monday – Rm 218 CLA I
Reading Summary /next exam
A
B
Battery with
internal R
C
W Wire
D
V=1.494,
Current
ma
Length – 30 cm units
PREVIOUS SLIDES ARE POSTED ON THE WEBSITE
Find the magnitude and direction of the current in the 2.0Ω resistor in the drawing. (Let R = 3.0 Ω and V = 2.5 V.)
=2.5
=3 ohm
A portable CD player operates with a voltage of 4.5 V, and its power usage is 0.21 W. What is the current in the player?
An especially violent lightning bolt has an average current of 1.15 103 A lasting 0.146 s. How much charge is delivered to the ground by the lightning bolt?
Two wires are identical, except that one is aluminum and one is iron. The aluminum wire has a resistance of 0.20 Ω. What is the resistance of the iron wire?
0.688Ω
The filament in an incandescent light bulb is made from tungsten. The light bulb is plugged into a 60 V outlet and draws a current of 0.96 A. If the radius of the tungsten wire is 0.0050 mm, how long must the wire be? 0.0877m
L
L1 L2
Series Resistors ADD
R
ABrighter
BDimmer
CNo Change
DIt goes out
EHuh??
TURN IN UNIT 5 NOW
Back To Work!!