Finding electromotive force

  • Thread starter joel amos
  • Start date
  • #1
104
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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?
 

Answers and Replies

  • #2
798
1
They asked what is the voltage that flows? Are you sure it wasn't current?
 
  • #3
104
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Not positive, but pretty sure.
 
  • #4
798
1
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.
 
  • #5
104
0
Is part "a" correct? And doesn't current remain constant?
 
  • #6
798
1
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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