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

In summary, the current through the inductor before the switch is opened can be calculated using the formula I=V/R, with V being the voltage and R being the resistance, resulting in a value of 55/150. The voltage in the right resistor before the switch is opened is irrelevant for a DC current, as the inductor acts as a wire. However, the current in the right resistor right after the switch is opened will depend on where the current in the inductor will now flow.
  • #1
amolv06
46
0
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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  • #2
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?
 
  • #3
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?

[tex] \frac{V}{R} = I[/tex] where I is 55/150?
 
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  • #4
Thanks, I completely mistyped that. 3 should read opened rather than closed.

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

[tex]I=V/R[/tex] where I = 55/150?
 
  • #5
amolv06 said:
Thanks, I completely mistyped that. 3 should read opened rather than closed.

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

[tex]I=V/R[/tex] where I = 55/150?

Yes, that is the answer
 

What is Kirchoff's Law?

Kirchoff's Law, also known as Kirchoff's Current and Voltage Laws, are fundamental principles in circuit analysis that describe the conservation of energy and charge in an electrical circuit.

How is Kirchoff's Law applied in an R-L circuit with parallel resistors?

In an R-L circuit with parallel resistors, Kirchoff's Current Law states that the current entering a junction is equal to the sum of the currents leaving the junction. Kirchoff's Voltage Law states that the sum of the voltage drops across the resistors in the parallel branch is equal to the voltage across the parallel branch.

What is the equation for Kirchoff's Current Law?

The equation for Kirchoff's Current Law is: ΣIin = ΣIout, where Σ represents the sum of all the currents entering or leaving a junction.

What is the equation for Kirchoff's Voltage Law?

The equation for Kirchoff's Voltage Law is: ΣVin = ΣVout, where Σ represents the sum of all the voltage drops across the resistors in a parallel branch.

Why is Kirchoff's Law important in circuit analysis?

Kirchoff's Law is important in circuit analysis because it allows us to calculate the unknown currents and voltages in a circuit by applying the principles of energy and charge conservation. It is also a fundamental concept that is used in more complex circuit analysis techniques, such as nodal and mesh analysis.

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