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DC Circuits
DC Circuits
Text sections 28.2, 28.3
•Series and parallel rules for resistors
•Kirchhoff’s circuit rules (maybe)
Practice:
Chapter 28, problems 3, 9, 11, 15, 21, 25, 28
“DC” Circuits
“DC” Circuits
“
Direct Current
”:
current always flows in one
direction.
(or,
often:
current is constant in time
)
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View Full Document Resistors in Series
Resistors in Series
R
1
R
2
R
3
...
3
2
1
+
+
+
=
R
R
R
R
eff
•S
am
e
c
u
r
r
e
n
t
through all resistors
• Voltages add:
∆
V =
∆
V
1
+
∆
V
2
+
∆
V
3
+ …
Î
IR
eff
= IR
1
+
2
+
3
+
…
So,
Resistors in Parallel
Resistors in Parallel
R
1
R
2
R
3
I
I
1
I
2
I
3
I
...
1
1
1
1
3
2
1
+
+
+
=
R
R
R
R
eff
• same voltage across each resistor
• currents add:
I = I
1
+ I
2
+ I
3
+ …
...
3
2
1
eff
+
∆
+
∆
+
∆
=
∆
⇒
R
V
R
V
R
V
R
V
so,
Example
Example
:
:
“Voltage Divider”
Circuit
“Voltage Divider”
Circuit
ε
R
1
R
2
V
1
V
2
V
V
R
R
R
V
×
+
=
2
1
1
1
V
R
R
R
V
×
+
=
2
1
2
2
and
Show that
Kirchhoff’s
Kirchhoff’s
Circuit Rules
Circuit Rules
Junction Rule
:
total current in = total current out
at each junction
(from conservation
of charge).
Loop Rule
:
Sum of
emfs
and
potential differences
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This note was uploaded on 12/03/2009 for the course CHEMISTRY 1E03 taught by Professor Britz during the Spring '09 term at McMaster University.
 Spring '09
 Britz

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