Applying Kirchoff's Law in an R-L circuit with parallel resistors

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Homework Help Overview

The discussion revolves around applying Kirchhoff's Law in an R-L circuit that includes parallel resistors. Participants are exploring the behavior of the circuit before and after a switch is opened, particularly focusing on current and voltage values in the circuit components.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning how to treat the parallel resistors in the circuit, particularly whether one of the resistors can be considered irrelevant. There is also discussion about the behavior of the inductor in a DC circuit and the implications of closing and opening the switch on current flow.

Discussion Status

The discussion is ongoing, with participants clarifying their understanding of the problem and correcting previous statements. Some guidance has been offered regarding the treatment of the inductor and the relevance of the resistors, but no consensus has been reached on the implications of these points.

Contextual Notes

There are indications of confusion regarding the phrasing of the problem, particularly in the interpretation of when the switch is opened or closed. This has led to corrections in the statements made by participants.

amolv06
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http://img296.imageshack.us/img296/6961/circuithk7.jpg

Assume that the switch has been closed a long time.

1.) Find the current through the inductor before the switch is opened.
2.) Find the voltage in the right resistor before the switch is opened.
3.) Find the current in the right resistor right after the switch is closed.

My question here is how do you treat both resistors? My hunch tells me that the right resistor is irrelevant, and that loop should be treated as superfluous, but I'm not sure. If anyone could answer that question, I would greatly appreciate it. Thanks.
 
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I think 3.) should end in "After the switch is opened".

For a DC current, an inductor is just a wire. This makes the exact value of the right resistor indeed irrelevant.

for 3.) I can't say that the right loop is irrelevant. What happens to the current in the inductor right after you close the switch? where will this current now go?
 
Thanks, I completely mistyped that. 3 should read opened rather than closed.

Just to clarify, the answer to #1 then should look like the following?

\frac{V}{R} = I where I is 55/150?
 
Last edited:
Thanks, I completely mistyped that. 3 should read opened rather than closed.

Just to clarify, the answer to #1 should be:

I=V/R where I = 55/150?
 
amolv06 said:
Thanks, I completely mistyped that. 3 should read opened rather than closed.

Just to clarify, the answer to #1 should be:

I=V/R where I = 55/150?

Yes, that is the answer
 

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