Calculating Electromotive Force in a Circuit

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Homework Help Overview

The discussion revolves around calculating the electromotive force (emf) in a circuit involving a battery with given internal resistance and load resistance. The problem includes determining both the emf and the voltage in the circuit.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the original poster's calculations for emf and voltage, questioning the phrasing of the problem regarding "voltage that flows" versus "current." There is also a focus on the consistency of current in a series circuit and the interpretation of voltage in this context.

Discussion Status

Some participants express confidence in the calculations provided for part a, while others seek clarification on terminology and concepts related to voltage and current. The conversation indicates a productive exploration of definitions and interpretations without reaching a definitive consensus.

Contextual Notes

There is a mention of the original poster being new to the concept of emf, which may influence their understanding and the nature of the questions being raised.

joel amos
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Homework Statement


A battery has a current of 3.0A flow through it. It has an internal resistance of 0.039Ω and the circuit has a load of 45Ω.
a) What is the emf?
b) What is the voltage that flows?

Homework Equations


V = ε - IR

The Attempt at a Solution


ε = V + IR
ε = (45Ω)(3A) + (3A)(0.039Ω)
ε = 135V + 0.117V

a) 135.117V
b) 135V

I'm new to emf. Does this look correct? If not, can you explain where I went awry?
 
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They asked what is the voltage that flows? Are you sure it wasn't current?
 
Not positive, but pretty sure.
 
I would check that. The voltage in a circuit doesn't "flow". The purpose of a battery is to keep the potential difference across two points in a circuit at a specific potential difference.
 
Is part "a" correct? And doesn't current remain constant?
 
Your answer looks good for part a. The current is the same everywhere in a series branch in a circuit. However, current refers to a collection of charges passing through a unit area in time t. Hence, it is often said to "flow".
 

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