Calculating resistance from voltage drop

AI Thread Summary
To calculate the resistance of a component using voltage drop, measure the voltage across the resistor and apply Ohm's law (R = E/I) to find the current through the circuit. In a series circuit, the current remains constant, allowing for the calculation of the lightbulb's resistance by measuring its voltage drop. Once the voltage across the lightbulb is known, use the same formula (R = E/I) to determine its resistance. This method effectively utilizes the known values of voltage and current to find the unknown resistance. Understanding these principles is essential for solving circuit problems in physics.
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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