Current through the circuit with resistor and light bulb

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SUMMARY

The discussion centers on calculating the current through a series circuit containing a resistor and a light bulb. The equation V=IR is applied, with an initial assumption of 0.45 Ω resistance for the bulb. However, the correct resistance is variable and described by a graph, leading to a calculated current of 0.3 A. Participants suggest using an iterative graphical approach to refine the lamp resistance until convergence is achieved.

PREREQUISITES
  • Understanding of Ohm's Law (V=IR)
  • Knowledge of series circuits
  • Familiarity with variable resistance concepts
  • Ability to interpret graphical data
NEXT STEPS
  • Study iterative methods for solving circuit problems
  • Learn about variable resistors and their applications
  • Explore graphical analysis techniques in electrical circuits
  • Review series circuit principles and calculations
USEFUL FOR

Students studying electrical engineering, educators teaching circuit analysis, and hobbyists interested in practical circuit design and analysis.

ashyau
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Homework Statement



Problem is give in the image


Homework Equations



V=IR

The Attempt at a Solution



Since its a series circuit i tried that current should be the same so it's 9/20 since there is no resistance in the bulb which is 0.45 Ω somehow the answer is 0.3Ω. why is that the case? should be something to do with the graph but i have no idea what to do with it
 

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In the image you've provided, it's difficult to tell what's being asked. I assume that you're supposed to finish the sentence: The current in the circuit is ______. Is that correct?
 
Last edited:
The resistance in the lamp is not zero. It is variable--described by the curved dashed line. The answer has units of "A", not "Ω". Try an iterative graphical approach--pick some starting value for the lamp resistance, say 20Ω, find the resulting current then use that current to determine a better value for lamp resistance. Repeat process until your lamp resistance converges.
 

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