# v3 i1 calculation what is i2 i3 label and pick

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Unformatted text preview: V3 ++ I1 Calculation What is I2 ?? I3 - Label and pick directions for each current Label the + and – side of each element Label This is easy for batteries For resistors, the “upstream” side is + For Now write down loop and node equations Physics 212 Lecture 10, Slide 11 11 V1 R1 ++ - -+ + R3 - - V2 R2 I2 - V3 ++ I1 Calculation BB In this circuit, assume Vi and Ri are known. What is I2 ?? I3 - • How many equations do we need to write down in order to solve for I2? (A) 1 (B) 2 (B) (C) 3 (C) (D) 4 (E) 5 • Why?? – – We have 3 unknowns: I1, I2, and I3 We need 3 independent equations to solve for these unknowns Physics 212 Lecture 10, Slide 12 12 V1 R1 ++ - -+ + R3 - - V2 R2 I2 - V3 ++ I1 Calculation I3 - BB In this circuit, assume Vi and Ri are known. What is I2 ?? • Which of the following equations is NOT correct? (A) (B) (C) (D) I2 = I1 + I3 - V1 + I1R1 - I3R3 + V3 = 0 - V3 + I3R3 + I2R2 + V2 = 0 - V2 – I2R2 + I1R1 + V1 = 0 • Why?? – – (D) is an attempt to write down KVR for the top loop Start at negative terminal of V2 and go clockwise • Vgain (-V2) then Vgain (-I2R2) then Vgain (-I1R1) then Vdrop (+V1) Physics 212 Lecture 10, Slide 13 13 R1 V1 R2 V2 R3 V3 I1 Calculation I2 BB In this circuit, assume Vi and Ri are known. I3 • We have the following...
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## This note was uploaded on 02/09/2012 for the course PHYSICS 212 taught by Professor Mestre during the Spring '11 term at University of Illinois at Urbana–Champaign.

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