Could Somebody help me please? EMF in parallel

  • Thread starter Thread starter Drakon25th
  • Start date Start date
  • Tags Tags
    Emf Parallel
Click For Summary

Homework Help Overview

The discussion revolves around a circuit problem involving two resistors (22 ohm and 15 ohm) and two electromotive forces (emfs). The original poster seeks assistance in determining the current through the resistors, particularly in the context of a parallel circuit and the presence of a second emf.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply Kirchhoff's loop law to derive equations for the currents in the circuit but encounters difficulties with the second emf and the relationship between the currents. Some participants question the sign of the terms in the equations and suggest alternative formulations. Others propose writing additional equations to account for all paths in the circuit.

Discussion Status

Participants are actively engaging with the problem, offering corrections to the original equations and suggesting new approaches. There is a collaborative effort to clarify the relationships between the currents and the effects of the two emfs, although no consensus has been reached on the final approach.

Contextual Notes

The original poster mentions uncertainty regarding the incorporation of the second emf and the total current in the parallel circuit. There is also a reference to the assumptions made about the direction of current flow.

Drakon25th
Ok, the question says: "Find the magnitudes and directions of the current through the 22 ohm and 15 ohm resistors (the internal resistance of the batteries is negligible)"

My question is how do i determine this if there's a second emf in the problem?

here's a picture of the problem:
picture

i tried using Kirchoff's loop law at first, first determining these two formulas:
0=E1-I1R1-I2R2
=9.0 - 22I1 - 15I2
I1 = .41 - .68I2

and

0=E2 - I2R2
= 6-15I2
I2 =.40

The problem is the second equation doesn't incorporate I3, so i can't use I3 = I2 + I1, so I'm stuck here.
Then I thought about using Ohm's law, but I am not sure how do i use E1 in terms of the parallel circuit to determine the total current going through the whole circuit. Please help me someone :smile:
 
Physics news on Phys.org
by the way, the directions for I1, I2, and I3 in the picture are my predictions on the current flow throughout the circuit
 
bump, please help me =(
 
I'm no electrical engineer, but...

It seems to me that given your choices for current flow (and I am presuming you are using conventional current, which imagines that a positive charge is what is flowing), your first equation has a bogus sign and should be:

0=E1-I1R1+I2R2.

Does it help to write another equation based on the third path of flow? That is the one with the two batteries and R1 in it:

E1+E2=I1R1.

That would allow you to immediately solve for I1. Then You could put that value in my corrected version of your first equation and solve for I2.
 
Last edited:
so there would be no I3?
 
If my analysis is correct, then it gives you I1 and I2, and as you said, you can then get I3 by adding those two: I3 = I2 + I1.
 
alright, thank you so much for the help :)
 

Similar threads

  • · Replies 18 ·
Replies
18
Views
4K
Replies
16
Views
2K
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
Replies
22
Views
5K
  • · Replies 1 ·
Replies
1
Views
2K