Finding Thevenin Equivalent Resistance: Circuit Analysis and Solution

[garr6120]

Homework Statement

given the circuit shown below find the the vanin equivalent at resistance R.

Homework Equations

the resistances on the right side of the circuit can be simplified: 18 || (24+12) = 12 kΩ.

The voltage can be found from 2 mA * 12 kΩ = 24 V.

The voltage V_a = 12-24 = -12 V

The Attempt at a Solution

When using multisim and the multimeter within the program it tells me the voltage of the open circuit is 36V.

Can anyone help me out?

 

[cnh1995]

The voltage can be found from 2 mA * 12 kΩ = 24 V.

With what polarity? Assume the bottom wire to be at 0V.

 

[garr6120]

With what polarity? Assume the bottom wire to be at 0V.

- V_2Ω + with the - charge facing the 0V wire

 

[cnh1995]

- V_2Ω + with the - charge facing the 0V wire

What is V_2Ω?

What is the polarity of the bottom of the 12k resistance if the current through it goes from bottom to top?

 

[garr6120]

What is V_2Ω?

What is the polarity of the bottom of the 12k resistance if the current through it goes from bottom to top?

+ to - from left to right.

 

[cnh1995]

+ to - from left to right.

I was talking about the equivalent resistance of the three resistors in the rightmost loop, which is 12k ohm. Draw this simplified circuit and find the polarity of the resistor terminal connected to the 0V point.

 

[garr6120]

I was talking about the equivalent resistance of the three resistors in the rightmost loop, which is 12k ohm. Draw this simplified circuit and find the polarity of the resistor terminal connected to the 0V point.

 

[cnh1995]

View attachment 212590

The current source is of 2mA, and you need to find the open circuit voltage. You have instead short-circuited the resistance R.

 

[garr6120]

The current source is of 2mA, and you need to find the open circuit voltage. You have instead short-circuited the resistance R.

 

[cnh1995]

View attachment 212595

The polarity of the resistor voltage is wrong. Conventional current flows from higher potential to lower potential.

 

[garr6120]

The polarity of the resistor voltage is wrong. Conventional current flows from higher potential to lower potential.

Even if it is i can correct it when I am done because its an arbitrary polarity. If i get negative for my answer I have to flip the polarity at the end so that if i recalculate my final answer the answer will be positive. So its just a prior guess right now.

but here it is.

 

[cnh1995]

but here it is.

That is correct. So now you can see why the answer is 36V.

 

[garr6120]

That is correct. So now you can see why the answer is 36V.

I thought the 12 V source wouldn't receive any current because of the open circuit.

Should I use KVL because when i make a loop at the open circuit i get:
-24V-2mA*12Ω=-12V