I need to calculate the equivalent resistance

In summary, the conversation discusses the calculation of equivalent resistance between points A and B in a circuit shown in "Fig.4". The speaker initially suggests that the first resistor is shorted by a wire connected between A and E, but another member corrects this by pointing out that the wire actually connects to another resistor. The conversation then suggests renaming nodes and coloring wires to clarify which points are connected. Finally, the number of nodes in the circuit is determined to be 3 and the speaker is advised to redraw the circuit accordingly.
  • #1
SaiTatter
2
1

Homework Statement


The circuit is the one in "Fig.4"
dTMsA0n.jpg

I need to calculate equivalent resistance between A and B. This is what I've tried:
w0ZCnUq.jpg

I think that the first resistor is shorted by that wire connected between A and E. Their answer looks like this, in fig 2.2.1. I'm not sure if their answer is wrong, or my idea about electricity has flaws. Thanks in advance for the explanations!
jrpmShY.jpg
 

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  • #2
Welcome to the PF. :smile:

Their answer/figure is correct. Just notice how point "A" connects to one side of those 3 R resistors, and the other side of each of those 3 R resistors are all connected together.
 
  • #3
Thanks berkeman! So proud to be here :).
 
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Likes berkeman
  • #4
Glad to help. :smile:
 
  • #5
[QUOTE="SaiTatter]
I think that the first resistor is shorted by that wire connected between A and E.[/QUOTE]

That's not correct. The wire doesn't connect one side of the resistor to the other side. It connects it to another resistor.

Note that some nodes (eg A and E) are connected together by wire so they are really the same electrical node. Try renaming node E to node A. Likewise for any other nodes that have two names. It might help to colour the wires so points that are connected together are the same colour.

How many different nodes are there? The answer only has 3.

Then redraw the circuit starting with a line of these 3 nodes. Then add the resistors between them.
 

FAQ: I need to calculate the equivalent resistance

What is equivalent resistance?

Equivalent resistance is a measure of the overall resistance of a circuit, taking into account all resistors in the circuit and their respective connections.

Why do I need to calculate equivalent resistance?

Calculating equivalent resistance allows you to determine the total resistance in a circuit, which is necessary for determining the amount of current flowing through the circuit.

How do I calculate equivalent resistance?

To calculate equivalent resistance, you can use the formula R = R1 + R2 + R3 + ..., where R represents the equivalent resistance and R1, R2, R3, etc. represent the individual resistances in the circuit. Alternatively, you can use the parallel or series resistance formulas depending on the circuit configuration.

Can equivalent resistance be greater than the sum of individual resistances?

Yes, in a parallel circuit, the equivalent resistance will always be less than the smallest individual resistance, and in a series circuit, the equivalent resistance will always be greater than the sum of the individual resistances.

What are the units of equivalent resistance?

The units of equivalent resistance are ohms (Ω), which is the standard unit of measurement for electrical resistance.

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