# Solving a Circuit with Nodal Analysis

• Engineering
• hdp12
In summary: I found Vab by subtracting Vb from Va and then I divided that by my determined REQIn summary, someone please guide me in the correct direction?
hdp12

## Homework Statement

I'm in a lab and we have this circuit & question as part of the pre-lab

## The Attempt at a Solution

I began trying to use nodal analysis to get Va & Vb & to then use Vab to get the voltage and then the current but after doing what you can see above, I stopped because I think there is another way that I'm supposed to do it.
Someone please guide me in the correct direction?
Thank you
H

hdp12 said:
I stopped because I think there is another way that I'm supposed to do it.
Make a Thevenin equivalent for ( R2 and R3 ) and for ( R1 and R4 ).

Vth = Vb = 5V*R3/(R2+R3). ( R2 and R3 is simply a voltage divider ).
Rth = R2 || R3. ( || means in parallel ).

Short circuit the two Thevenin equivalents to find Isc.

REQ = Rth + Rth.

You're looking for the short circuit current, so essentially the current flowing through a wire (replacing RL with a wire). My first instinct would be to use mesh analysis to find that current, but a niftier choice would be to work with what you've already got and proceed to find the Thevenin equivalent (or Norton equivalent), since really all you need to finish is the equivalent resistance of the circuit looking into the open load terminals; The network is not difficult to simplify. Then finding the short circuit current would be trivial.

okay, using what both of you said, I tried to finish the problem. Tell me what you think,

You were doing fine until you went to calculate ISC. It's not clear from your work what values you are using for Vth and Rth. What comprises your final equivalent circuit?

I determined Vab by subtracting Vb from Va and then I divided that by my determined REQ

hdp12 said:
I determined Vab by subtracting Vb from Va and then I divided that by my determined REQ
Okay, can you check (and post) the values?

## 1. What causes a short circuit?

A short circuit occurs when there is a direct connection between the positive and negative terminals in an electrical circuit. This can be caused by damaged wires, faulty components, or incorrect wiring.

## 2. How do I know if I have a short circuit?

The most common signs of a short circuit include flickering lights, blown fuses, or a tripped circuit breaker. You may also notice a burning smell or see sparks or smoke coming from an outlet or appliance.

## 3. Can a short circuit be dangerous?

Yes, short circuits can be dangerous as they can cause electrical fires or damage to appliances and equipment. It is important to address any suspected short circuits immediately to prevent potential hazards.

## 4. How do I fix a short circuit?

The first step in fixing a short circuit is to identify and remove the source of the problem, such as damaged wires or faulty components. If you are unsure how to do this, it is best to seek the help of a professional electrician.

## 5. How can I prevent short circuits?

To prevent short circuits, make sure all electrical wiring and components are installed correctly and regularly inspect them for any signs of damage. Avoid overloading outlets and circuits, and use surge protectors to protect against power surges.

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