How Do You Calculate Thevenin Equivalent Circuit Without a Load Resistor?

[Alexander Max]

Homework Statement

I am to find the thevenin equivalent circuit without the load resistor (to the left of terminals a &b

Homework Equations

From class notes:
1- Remove the load resistor
2- find the open circuit voltage across a & b
3- Remove all voltage sources (replace with short circuit)
4- Detrmine the equivalent circuit resistance across the break
5- Form an equivalent circuit

The Attempt at a Solution

I have not come across the symbol that looks like an 8 with the 2amps next to it so far, and i don't understand how this will effect my circuit, is it a voltage source, how will it effect the resistors?
Without acknowledging it,
my resistors are all in parralel so Restance total is
1/RT = 1/R1 + 1/R2 + 1/R3
1/RT = 1/4 + 1/12 + 1/1
1/RT = 3/12 + 1/12 + 12/12
1/RT = 16/12
RT = 12/16
RT = 0.75

32v/0.75 ohms = 42.667 Amps
Vab = 32 - 1x42.667Amps = -10.667 Volts

Resistance looking in has already been calulated as 0.75 ohms

 

[BvU]

Hello Alex, and welcome to PF :)

The 2A thingy is a (slightly outdated) symbol for a current source.

I don't see how you can consider all R as parallel.

 

[gneill]

Hi Alexander Max, Welcome to Physics Forums.

As BvU stated, the two-circle symbol represents a current source. It's a bit outmoded as a schematic symbol, but it still crops up fairly often.

Allow me to amend your algorithm's item 3 a bit, since in its given form it doesn't address current sources:

3 - Suppress all independent sources: Replace voltage sources with a short circuit and all current sources with an open circuit (simply remove them entirely).

 

[Alexander Max]

Thank you for your help!

 

[HalfLostAndSearching]

Hello,

Thevenin's theorem is a useful tool for simplifying complex circuits and determining the equivalent circuit for a specific load. To find the Thevenin equivalent circuit without the load resistor, you will follow the steps outlined in your class notes.

First, remove the load resistor and find the open circuit voltage across terminals a and b. Next, remove all voltage sources and replace them with short circuits. This will effectively remove the 8 with 2 amps symbol, as it is a voltage source. The resistors will not be affected by this, as they are only affected by the voltage and current in the circuit.

Next, determine the equivalent circuit resistance across the break. In this case, the resistors are in parallel, so the total resistance will be 0.75 ohms.

Finally, you can form the equivalent circuit by combining the open circuit voltage and the equivalent resistance. The result will be a voltage source of -10.667 volts in series with a resistor of 0.75 ohms.

I hope this helps clarify the steps for finding the Thevenin equivalent circuit without the load resistor. Let me know if you have any further questions. Good luck with your homework!