Current Through R1 and R3: Explained

In summary, in the second picture, R2 will cancel out because it is shorted. This happens when you have a branch containing components parallel with a wire.
  • #1
archaic
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Moved from a technical forum, no template.
Hey guys, in the picture below, the current flowing through R1 is the same flowing through R3 right? And hence we have R1 and R3 in series?
th3.png

In this second picture R2 is going to cancel out because apparently that's what happens when you have a branch containing components parallel with a wire, why is that?
th4.png
 

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  • #2
archaic said:
Hey guys, in the picture below, the current flowing through R1 is the same flowing through R3 right? And hence we have R1 and R3 in series?
Right, assuming that there are no circuit elements beyond points A and B.
archaic said:
In this second picture R2 is going to cancel out because apparently that's what happens when you have a branch parallel with a wire, why is that?
That's because R2 is shorted, i.e. the potential difference across it zero (think of the straight wire as an equipotential). Ohm's Law says V = IR. Here, V = 0 therefore I = 0 and R2 draws no current, assuming that there is a potential difference between A and B.
 
  • #3
Please use the homework forum, and please fill out the template provided when you create a homework thread.

In the top diagram, provided that A-B is open circuit (no current), then the answer is yes. You are correct.

archaic said:
In this second picture R2 is going to cancel out because apparently that's what happens when you have a branch parallel with a wire, why is that?
How much current flows through R2 in the second picture?
 
  • #4
kuruman said:
Right, assuming that there are no circuit elements beyond points A and B.
Yes, it's an open circuit, but this is part of a Thevenin's theorem exercise so we're assuming there's an open circuit voltage at the terminals A and B.

kuruman said:
That's because R2 is shorted, i.e. the potential difference across it zero (think of the straight wire as an equipotential). Ohm's Law says V = IR. Here, V = 0 therefore I = 0 and R2 draws no current, assuming that there is a potential difference between A and B.
anorlunda said:
How much current flows through R2 in the second picture?
Well as kuruman said the current is 0, the explanation we were given is "the current takes the less difficult path" but how would it know which one it is?
 
  • #5
archaic said:
Well as kuruman said the current is 0, the explanation we were given is "the current takes the less difficult path" but how would it know which one it is?
Well, how much resistance is there in a short circuit?
 
  • #6
phinds said:
Well, how much resistance is there in a short circuit?
0 of course.
 
  • #7
archaic said:
0 of course.
And you are having a hard time figuring out whether this is less than R2?
 
  • #8
phinds said:
And you are having a hard time figuring out whether this is less than R2?
No but I want to know how electrons figure it out before going through the wire.
 
  • #9
Change it a bit. Think of the wire in parallel with R2 as having resistance R4. Then calculate the equation for R2 in parallel with R4. Then set R4=0, how much is resistance is R2 in parallel with R4?
 
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FAQ: Current Through R1 and R3: Explained

1. What is current through R1 and R3?

The current through R1 and R3 refers to the flow of electric charge through resistors R1 and R3 in an electrical circuit. It is measured in amperes (A) and is determined by the voltage applied and the resistance of the resistors.

2. How is current calculated through R1 and R3?

The current through R1 and R3 can be calculated using Ohm's law, which states that current (I) is equal to the voltage (V) divided by the resistance (R). So, I = V/R. This means that the current will increase as the voltage increases and decrease as the resistance increases.

3. Why is current through R1 and R3 important?

Current through R1 and R3 is important because it helps determine the overall flow of electricity in a circuit. It also affects the amount of power dissipated in the resistors and can impact the performance and safety of the circuit.

4. What happens if the resistance of R1 and R3 is changed?

If the resistance of R1 and R3 is changed, the current through these resistors will also change. This is due to the inverse relationship between resistance and current. As resistance increases, current decreases and vice versa.

5. How does the current through R1 and R3 affect other components in the circuit?

The current through R1 and R3 can affect other components in the circuit, especially if they are connected in series. The total current in a series circuit is equal throughout, so any changes in the current through R1 and R3 will also impact the current in the rest of the circuit. Additionally, the voltage drop across R1 and R3 can affect the voltage and performance of other components in the circuit.

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