Calculating Current in a Series Circuit with an LED

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Homework Help Overview

The discussion revolves around calculating the current in a series circuit that includes a resistor and an LED. Participants are exploring the relationships between voltage, current, and resistance in this context.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants attempt to calculate current using Ohm's law and discuss the implications of the series circuit configuration. Questions arise regarding the voltage across the resistor and how to treat the LED's voltage drop.

Discussion Status

The conversation is active, with participants providing insights into the nature of series circuits and confirming the constancy of current. Some guidance has been offered regarding the voltage across components, but no consensus on specific calculations has been reached.

Contextual Notes

There is uncertainty about the voltage across the resistor and how it relates to the total voltage in the circuit. Participants are also navigating the implications of the LED's voltage drop in their calculations.

Marcin H
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Homework Statement


Screen Shot 2016-02-04 at 11.54.34 AM.png


Homework Equations


V=IR

The Attempt at a Solution


I'm not sure if this is right, but I did this problem by finding the current in the 300ohm resistor by doing I=5V/300ohms = .0166A and since they are in series they have the same current. I don't think that is right though. The LED is 2V, so I'm not sure how to treat that.
 
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Marcin H said:

Homework Statement


View attachment 95288

Homework Equations


V=IR

The Attempt at a Solution


I'm not sure if this is right, but I did this problem by finding the current in the 300ohm resistor by doing I=5V/300ohms = .0166A and since they are in series they have the same current. I don't think that is right though. The LED is 2V, so I'm not sure how to treat that.

The voltage across the resistor is not 5 v. What type of circuit is this (series / parallel). What do you know about the voltage and current in that type of circuit?
 
Jake 7174 said:
The voltage across the resistor is not 5 v. What type of circuit is this (series / parallel). What do you know about the voltage and current in that type of circuit?
It's a series circuit right? In series current is the same throughout the circuit and voltage is different. For parallel voltage is the same and current is different.
 
Marcin H said:
It's a series circuit right? In series current is the same throughout the circuit and voltage is different. For parallel voltage is the same and current is different.
Right. What is the voltage across resistor then?
 
cnh1995 said:
Right. What is the voltage across resistor then?
Im not sure. Would it be 3V? Va-Vb?
 
Marcin H said:
Im not sure. Would it be 3V? Va-Vb?

Good, Now, What is the current through the resistor
 
Jake 7174 said:
Good, Now, What is the current through the resistor
.01A. So does that mean that .01A are flowing through the LED?
 
Marcin H said:
.01A. So does that mean that .01A are flowing through the LED?
Yes.
 
Marcin H said:
.01A. So does that mean that .01A are flowing through the LED?

In a series circuit is current constant?
 
  • #10
Jake 7174 said:
In a series circuit is current constant?
Yes. same current, different voltage.
 
  • #11
Marcin H said:
Yes. same current, different voltage.

There you go. Good job!
 
  • #12
Jake 7174 said:
There you go. Good job!
Thanks!
 

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