Ohm's Law - Finding Source Voltage

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Homework Help Overview

The discussion revolves around determining the source voltage in a DC series circuit given specific resistor values and a known voltage drop across one of the resistors. The original poster presents the values of three resistors and the voltage drop across the first resistor, seeking to understand how to calculate the total source voltage.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the total resistance and current based on the given resistor values and voltage drop, but expresses confusion about the results. Some participants question the calculations and the assumptions made regarding the circuit parameters.

Discussion Status

Participants are engaging in clarifying the relationships between voltage, current, and resistance in the context of Ohm's Law. There is an ongoing exploration of the implications of the voltage drop and how it relates to the overall circuit behavior, with no explicit consensus reached yet.

Contextual Notes

The original poster is working under the constraints of a homework problem, which may limit the information available for calculations. The discussion includes questioning the accuracy of the initial assumptions and calculations regarding the circuit's total resistance and current.

Brian82784
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TL;DR Summary: Ohms Law Source Voltage DC series Circuit

Hello,

I'm trying to figure out how to determine source voltage of a DC series circuit. The only information given is

Resistor 1 = 12ohm
Resistor 2 = 9ohm
Resistor 3 = 3ohm

And the voltage drop across R1 is 6V.

The answer is 12V for the DC battery. But I can't figure out how to get to 12.

If I put 12V down as the battery size, and combine all three resistors 24ohm and use ohms law I can't come up with 12V.

R total = 24ohm
12V source battery

24 divided by 12 = 2Amps

Now if I go to R1 and knowing that the circuit amperage is 2, I get a voltage drop of 2A * 12ohm = 24V not 6V.

Where am I going wrong?
 
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Brian82784 said:
24 divided by 12 = 2Amps
Reminder: V=IR :wink:
 
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Likes   Reactions: Gavran
Brian82784 said:
And the voltage drop across R1 is 6V.
So this gives you the current through R1, and hence that same current flows through all 3 series resistors. :smile:
 
Brian82784 said:
Resistor 1 = 12ohm

And the voltage drop across R1 is 6V.
So what is the current?
 

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