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Unformatted text preview: ure 10, Slide Calculation: Simplify
In this circuit, assume V and R are known. What is I2 ??
R
2R
R 2V
V
V I1
I2 • We have 3 equations and 3 unknowns.
I2 = I1 + I3
2V + I1R I3R + V = 0 (outside)
V – I2(2R) I1R + 2V= 0 (top) I3
current
current
direction
direction • With this simplification, you can verify:
I2 = ( 1/5) V/R
I1 = ( 3/5) V/R
I3 = (2/5) V/R Physics 212 Lecture 10, Slide 20
Physics 212 Lecture 10, Slide 2V R V 2R
a I1 • We know: I2 = ( 1/5) V/R
I1 = ( 3/5) V/R
I3 = (2/5) V/R I2 b R • FollowUp V I3 Suppose we short R3: What happens to Vab (voltage across R2?) (A) Vab remains the same Why?
(B) Vab changes sign Redraw:
(C) Vab increases
(D) Vab goes to zero
Bottom Loop Equation: Vab + V – V = 0
Vab = 0 R
2R
a 2V
V
b
c V I1
I2 d I3 Physics 212 Lecture 10, Slide 21
Physics 212 Lecture 10, Slide A V B R R Is there a current flowing between A and B ?
A) Yes
B) No
A & B have the same potential
Current flows from battery and splits at A No current flows between A & B
Some current flows down
Some current flows right Physics 212 Lecture 10, Slide 22
Physics 212 Lecture 10, Slide Checkpoint 3a Consider the circuit shown below. Note that this question is not identical to the similar looking one
I1
I2
you answered in the prelecture. Which of the following best describes the current flowing in the blue wire connecting points a and b?
A. Positive current flows from a to b
B. Positive current flows from b to a
C. No current flows between a and b “Energy flows toward least resistance, which is 1R.”
“because b has higher voltage than a”
“The top half is the same as the bottom half.”
Physics 212 Lecture 10, Slide 23
Physics 212 Lecture 10, Slide Checkpoint 3a Consider the circuit shown below. Note that this question is not identical to the similar looking one
I1
I2
you answered in the prelecture. I1 I I2 I4 I3 Which...
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This note was uploaded on 02/18/2013 for the course PHYS 212 taught by Professor Kim during the Fall '08 term at University of Illinois, Urbana Champaign.
 Fall '08
 Kim
 Physics

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