Find the current

  • Thread starter Gauss M.D.
  • Start date
  • #1
153
1

Homework Statement



Find the current marked I3 in the circuit.

Homework Equations





The Attempt at a Solution



The voltage over R2 and R1 is the same. The current I0 (12mA) is the sum of I2 and I1.

I1*R1 = I2*R2:
4*I1 = 1.25*I2

I1 + I2 = 12 <=> I2 = 12 - I1

4*I1 = 1.25*(12 - I1) = 15 - 1.25I1
5.25*I1 = 15

I1 = 2.86

I think I've messed up already here. Can anyone spot what I'm doing wrong??
 

Attachments

  • circ1.png
    circ1.png
    8.7 KB · Views: 387

Answers and Replies

  • #2
ehild
Homework Helper
15,543
1,915

Homework Statement



Find the current marked I3 in the circuit.

Homework Equations





The Attempt at a Solution



The voltage over R2 and R1 is the same. The current I0 (12mA) is the sum of I2 and I1.

I1*R1 = I2*R2:
4*I1 = 1.25*I2

It is wrong. The voltage over R3 and R4 is the same .

I1 + I2 = 12 <=> I2 = 12 - I1

4*I1 = 1.25*(12 - I1) = 15 - 1.25I1
5.25*I1 = 15

I1 = 2.86

I think I've messed up already here. Can anyone spot what I'm doing wrong??
 
  • #3
153
1
Thanks! Is I2 still the sum of I3+I4 though? :S
 
  • #4
gneill
Mentor
20,945
2,886

Related Threads on Find the current

  • Last Post
2
Replies
40
Views
2K
  • Last Post
Replies
8
Views
857
  • Last Post
Replies
4
Views
12K
  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
7
Views
977
  • Last Post
Replies
19
Views
1K
  • Last Post
Replies
5
Views
2K
Replies
1
Views
2K
Replies
1
Views
2K
  • Last Post
Replies
5
Views
2K
Top