Find Current I3 in Circuit - Homework Statement

  • Thread starter Thread starter Gauss M.D.
  • Start date Start date
  • Tags Tags
    Current
Click For Summary
To find the current I3 in the circuit, the user notes that the voltage across resistors R1 and R2 is the same, and the total current I0 is 12mA, which equals the sum of currents I1 and I2. The user sets up the equation relating the currents through the resistors, but realizes there may be an error in their calculations. They calculate I1 as 2.86mA but express uncertainty about the correctness of their approach. The discussion also raises the question of whether I2 is the sum of currents I3 and I4.
Gauss M.D.
Messages
151
Reaction score
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
    4.4 KB · Views: 474
Physics news on Phys.org
Gauss M.D. said:

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 .

Gauss M.D. said:
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??
 
  • Like
Likes 1 person
Thanks! Is I2 still the sum of I3+I4 though? :S
 
Gauss M.D. said:
Thanks! Is I2 still the sum of I3+I4 though? :S

Sure.
 

Thread 'Magnitude of buoyant force in fluids of different densities'

The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?
View full post »

Similar threads

Network Analysis, Kirchhoff's Laws, changing current source to voltage
  • · Replies 4 ·
Replies
4
Views
1K
Solving Current & Power in 4 & 3 Wire Circuits
  • · Replies 9 ·
Replies
9
Views
2K
Using Kirchhoff's laws on this current division problem
  • · Replies 12 ·
Replies
12
Views
2K
Kirchhoff's law: Find the current I3 through the Amp meter
  • · Replies 4 ·
Replies
4
Views
2K
Power dissipated in this circuit with 2 batteries and 3 resistors
  • · Replies 22 ·
Replies
22
Views
4K
Finding the currents in this circuit (2 voltage sources and 3 resistors)
  • · Replies 10 ·
Replies
10
Views
3K
Did I count this current in a circuit correctly?
  • · Replies 6 ·
Replies
6
Views
2K
Writing Kirchhoff Rules for a Multi-Loop Circuit
  • · Replies 5 ·
Replies
5
Views
3K
How Do Kirchhoff's Laws Help Calculate I1, I2, and I3 in a Circuit?
  • · Replies 1 ·
Replies
1
Views
1K
Find the transient current in this circuit
  • · Replies 31 ·
2
Replies
31
Views
3K