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Find and calculate current in a circuit

  • Thread starter choco_moo
  • Start date
  • #1
26
0

Homework Statement


Consider the following configuration.
2yy341e.gif

Given:
EMF1=6 V
EMF2 = 3 V
R1 = 600 Ohm
R3 = 100 Ohm

1. Calculate the current i1.
2. Calculate the current i3.


Homework Equations


V=IR
Kirchoff's circuit laws:
1. Sum of current into any node is zero.
2. Sum of voltages around any loop is zero.


The Attempt at a Solution


I know that the potential at point A is 6 V because of the battery. I can't figure out how to calculate i1. I think I somehow have to use Kirchoff's rule, but I just don't know how. I tried to set up a voltage equation: EMF1 -i1R1 - i3R3 = 0. I don't know if that's right but it still has two unknowns. For i3, it seems like I have to know what i1 is to calculate it. Any help is appreciated!
 

Answers and Replies

  • #2
rl.bhat
Homework Helper
4,433
7
This voltage equation: EMF1 -i1R1 - i3R3 = 0. is correct.
Write down similar equation for EMF2. Put i3 = i1 + i2 and solve the equations to find i1 and i2.
 
  • #3
26
0
How would I know which resistor i2 corresponds to?
 
  • #4
rl.bhat
Homework Helper
4,433
7
EMF2 - (i1 + i2)R3 = 0.
 
  • #5
26
0
Ah, that makes sense. So I set those two voltage equations equal to each other and solved for i1. Then I plugged i1 into the EMF2 voltage equation and solved for i2. I finally added i1 and i2 together to get i3. Thanks so much!
 

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