Calculating resistance from voltage drop

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SUMMARY

The discussion centers on calculating the resistance of a lightbulb in a simple circuit using Ohm's Law. Participants emphasize measuring the voltage drop across the resistor and lightbulb to determine the current. By applying the formula R = E/I, where E is the voltage and I is the current, one can find the resistance of the lightbulb after measuring the voltage across it. This method is applicable in series circuits where the current remains constant.

PREREQUISITES
  • Understanding of Ohm's Law (R = E/I)
  • Ability to measure voltage using a voltmeter
  • Knowledge of series circuit principles
  • Familiarity with basic electrical components (resistors, lightbulbs)
NEXT STEPS
  • Research how to use a voltmeter effectively in circuit measurements
  • Study series circuit configurations and their properties
  • Learn about different types of resistors and their characteristics
  • Explore advanced applications of Ohm's Law in complex circuits
USEFUL FOR

Students in electrical engineering, hobbyists building circuits, and anyone looking to deepen their understanding of basic electrical principles and calculations.

EdTheHead
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On a test in college I was asked to find the current flowing through a resistor and lightbulb on a simple circuit with a battery, resistor and lightbulb. I was told the resistance of the resistor and was given a voltmeter so I measured the voltage across each of the components but when it came to calculating the current I couldn't because I didn't know the resistance of the lightbulb. I'm assuming I could have calculated its resistance since I knew the voltage drop caused by the resistor since I knew the resistance of the resistor. How would you go about calculating the resistance of a component when you know the voltage drop caused by it?
 
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Ohm's law.

R = E/I
 
EdTheHead said:
How would you go about calculating the resistance of a component when you know the voltage drop caused by it?

Measure the voltage across the resistor, then I = E/R. Now you know the current through the circuit if it is a series circuit. Measure the voltage across the light bulb, then apply R= E/I.
 

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