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EE201 Linear Circuit Analysis I
Lecture 8.
Topics:
Mesh (Loop) Analysis
1.
Loop (Mesh) Analysis – Basics
(1)
The concepts of loops, loop currents & branch currents
•
Loops
•
Loop currents:
I
1
, I
2
(may NOT be the actual current flowing in a branch).
•
Branch current I
L
= I
1
– I
2
(this is the ACTUAL current flowing in a branch).
•
Ohm’s Law applies to branch current, V
L
= I
L
· R.
•
Ohm’s Law may or may not apply to loop currents.
(2) How to write loop equations:
•
The goal of loop analysis is to find all the branch currents.
•
3 Steps:
Step 1 Use KVL to sum the voltages around a loop;
Step 2  Use Ohm’s law to express voltages in terms of loop currents;
Step 3  Use loop currents to compute branch currents.
Example
.
Loop 1:
+

↑
+
V
L
–
I
2
I
1
I
L
↓
R
L
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Loop 2:
What is V
L
?
(3)
What if we change the direction of I
2
(because of the current source)?