Current after passing all resistors

In summary, the current in the circuit is 0.129A, despite the fact that there is no voltage at point I.
  • #1
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Homework Statement



Find the current at point I:

[PLAIN]http://img690.imageshack.us/img690/8508/circuit.png [Broken]


Homework Equations


V=IR


The Attempt at a Solution


It seems there should be no current at point I, since there is no voltage. The total resistance in the circuit is 77 ohms. 10.0 V - (10.0 V/77 ohms)*(77)=0. However, the answer is supposedly 0.13 A. What is wrong with my reasoning?

Thanks in advance.
 
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  • #2
OK, so the the total resistance is 77 Ohms. If you put a 10V battery across 77 Ohms, how much current is provided by the battery? That's what the problem is asking.
 
  • #3
Oh, I see. But at that point, there would be no current, right? If there is no voltage, how can there be a current?
 
  • #4
No.

The current leaves the positive terminal of the battery and travels around the circuit through all the resistors (splitting equally when equal resistors are in parallel) and then exactly the same current arrives back at the negative terminal of the battery.
 
  • #5
Voltage is a potential difference between two points in a circuit. Between which two points are you saying there is no voltage? Also, if you agree that the battery provides a current, where do the electrons that leave the battery go?
 
  • #6
vk6kro said:
No.

The current leaves the positive terminal of the battery and travels around the circuit through all the resistors (splitting equally when equal resistors are in parallel) and then exactly the same current arrives back at the negative terminal of the battery.

kuruman said:
Voltage is a potential difference between two points in a circuit. Between which two points are you saying there is no voltage? Also, if you agree that the battery provides a current, where do the electrons that leave the battery go?

Shouldn't there be no potential difference between point I and the negative terminal of the battery since there is nothing to provide resistance or potential? In a real circuit there would be some resistance in the wire.

If there is no potential difference between these two points, how can there be a current (0=IR)?
 
  • #7
You have drawn these as two different points for convenience, but they are electrically the same point.

The current leaves the positive terminal of the battery and travels around the circuit through all the resistors (splitting equally when equal resistors are in parallel) and then exactly the same current arrives back at the negative terminal of the battery.
 
  • #8
Thank you, I think I understand now.
 
  • #9
V = IR so I = V/R, on substituting the values, we get 10/77, which 0.129A, which is the answer.
 

1. What is "current after passing all resistors?"

"Current after passing all resistors" refers to the amount of electrical current that is flowing through a circuit after it has passed through all of the resistors in that circuit. This current can be calculated using Ohm's law, which states that current is equal to the voltage divided by the total resistance in the circuit.

2. How do resistors affect the current in a circuit?

Resistors are components in a circuit that resist the flow of electrical current. This means that they limit the amount of current that can pass through them. The more resistors there are in a circuit, the lower the current will be.

3. Can current change after passing through resistors?

Yes, the current can change after passing through resistors. This is because resistors can be connected in series or parallel, which affects the total resistance in the circuit. If resistors are connected in series, the total resistance increases and therefore the current decreases. If they are connected in parallel, the total resistance decreases and the current increases.

4. How do I calculate the current after passing through all resistors?

To calculate the current after passing through all resistors, you can use Ohm's law. First, determine the total resistance in the circuit by adding up the resistances of all the individual resistors. Then, divide the voltage by the total resistance to find the current. You can also use Kirchhoff's circuit laws to calculate the current in more complex circuits.

5. What happens to the current if a resistor is removed from a circuit?

If a resistor is removed from a circuit, the total resistance in the circuit decreases and therefore the current increases. This is because there is less resistance to limit the flow of current. However, if the resistor was the only component in the circuit, there would be no current flowing through the circuit without it.

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