Find Current Through 40 Ohms Resistor Using Thevenin

In summary, you may be able to solve the circuit using a nodal analysis if you have the load resistor removed, or a mesh analysis if the current source is fixed.
  • #1
Special One
32
1
Homework Statement
current
Relevant Equations
ohm law
Find the current through the 40ohms resistor using the Thevenin?
I have calculated the Zth = 10 ohms. And I couldn't find the Vth.

Screenshot 2020-10-17 at 19.05.40.png
 
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  • #2
So what have you tried?
 
  • #3
gneill said:
So what have you tried?
Nodal method
 
  • #4
Special One said:
Nodal method
Okay, possibly not the simplest way forward but let's see your attempt. Where did you get hung up?
 
  • #5
gneill said:
Okay, possibly not the simplest way forward but let's see your attempt. Where did you get hung up?
I would prefer not to share it here because the correct answer doesn't match with my solution. Let's say you solving the problem, Can you tell what you're going to do to solve for Vth?
 
  • #6
Special One said:
I would prefer not to share it here because the correct answer doesn't match with my solution. Let's say you solving the problem, Can you tell what you're going to do to solve for Vth?
Sorry, that's not the way it works here at PF. You need to show your own efforts before we can offer guidance, which includes pointing out missteps in your attempt. No one here will do your homework for you.

If you show your attempted solution then we can spot where it might have gone wrong.
 
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  • #7
So @Special One if you take the Thevenin Equivalent as across the 40Ω resistor, you would remove that from the circuit, then figure the voltage between those 2 nodes. That is the Thevenin Voltage. Once you have that, then you draw a short circuit between the nodes, and calculate the current through that short.

To find the Thevenin equivalent resistance, just divide: (Thevenin Voltage) ÷ (short circuit current).

As others have said, the way PhysicsForums works, you put what you have attempted, and the other contributors will look and point out where you may have mistakes. That way, you can learn from your mistakes.

https://practicalee.com/thevenin-equivalent/#:~:text=Steps to Find the Thevenin and Norton Equivalent,and series reduction combinations. ... More items...
 
  • #8
  • #9
Special One said:
What next? How can I find Vth?
Above you mentioned attempting nodal analysis. You could show us that attempt, or consider another approach. Here's a thought that might get you thinking along other lines:

Looking at the circuit with the load removed you can pick out three essential nodes. That implies three equations in three unknowns for a nodal analysis approach. However, with the load resistor removed there are only two loops, so you're down to two equations and two unknows.

But it gets better! For a mesh analysis one of the loops has its mesh current fixed by the 10 A current source, so that loop is already solved and you're down to a single equation with one unknown. Find that current then do a little "KVL walk" between the output leads and you're done.
 
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1. What is Thevenin's Theorem?

Thevenin's Theorem states that any linear electrical network with voltage and current sources can be replaced by an equivalent circuit consisting of a single voltage source in series with a single resistor.

2. How do I find the Thevenin equivalent circuit?

To find the Thevenin equivalent circuit, you need to follow these steps:

  1. Remove the load resistor from the original circuit.
  2. Calculate the open-circuit voltage (VOC) across the load terminals.
  3. Calculate the equivalent resistance (REQ) seen from the load terminals.
  4. Draw the Thevenin equivalent circuit with VOC as the voltage source and REQ as the resistor.

3. What is the purpose of finding the Thevenin equivalent circuit?

The Thevenin equivalent circuit helps simplify complex networks and makes it easier to analyze and solve for the current and voltage in a specific part of the circuit. It also allows for easier replacement of components and prediction of circuit behavior under different load conditions.

4. How do I find the current through a specific resistor using Thevenin's Theorem?

To find the current through a specific resistor using Thevenin's Theorem, you need to follow these steps:

  1. Find the Thevenin equivalent circuit of the original circuit.
  2. Add the load resistor back into the circuit.
  3. Calculate the total resistance (RTOT) by adding the load resistor (RL) to the Thevenin equivalent resistance (REQ).
  4. Use Ohm's Law (I = V/R) to calculate the current (I) through the load resistor.

5. Can Thevenin's Theorem be applied to non-linear circuits?

No, Thevenin's Theorem can only be applied to linear circuits. Non-linear circuits have components that do not follow Ohm's Law, which is a fundamental requirement for Thevenin's Theorem to be applicable.

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