text: # Emf and Terminal Voltage
  
  nautica
  Okay here is the question:
  
  a) what is the internal resistance of a voltage source if its terminal voltage drops by 2 V when the current supplied increases by 5 A.
  
  b) Can the emf of the voltage source be found with the information supplied?
  
  I know that E = V - Ir, and I am pretty sure that a simple algebraic equation can be put together. So what formulat am I missing??
  
  Thanks
  Nautica
  
  Related Introductory Physics Homework Help News on Phys.org
  HallsofIvy
  Homework Helper
  You know that E = V - Ir so &Delta;E= &Delta;V- &Delta;I r. You are told that &Delta;E= 2volts when &Dekta;I= -5 amps. Of course, &Delta;V= 0 since the voltage source is fixed.
  Thatis: 2= -5r. Can you solve for r now? .
  
  The answer to b is NO. In effect V is the "constant of integration" when you "integrate" dE= -rdI. There is no way to find that from the information given.
  
  Last edited by a moderator:
  nautica
  I am in College Physics, we can not use calculus for an answer. So is there a reason algebraically.
  
  thanks
  nautica
  
  If u know the potential diff b/w two terminals, then u can find the emf.
  
  With this information u cannot find
  
  nautica
  So ther is no way to find emf without Potential difference???
  
  thanks
  nautica
  
  nautica
  Okay For a) here is what I got
  
  V=E-Ir
  
  or dV=dE - dIr
  
  2V = -5r
  
  so r = -.4Ohms
  
  BUT, my instructor said this was wrong b/c there I did not no the Rload and there are too many unknowns for this to be solved.
  
  I can see how part B could not be solved but this looked so simple for part a)
  
  He said this was the other equation I should have considered, but I do not see why it was needed.
  
  I = E / (Rload + r)
  
  Thanks
  nautica
explanation: The document contains a physics problem related to electromotive force (EMF) and terminal voltage. The user, nautica, asks two questions:
  
  a) What is the internal resistance of a voltage source if its terminal voltage drops by 2 V when the current supplied increases by 5 A?
  b) Can the emf of the voltage source be found with the information supplied?
  
  The user also provides their attempt at solving part (a) and mentions that their instructor indicated the solution was incorrect, suggesting the need to consider the load resistance.
  
  HallsofIvy provides a detailed response, explaining how to solve part (a) using the given formula and confirming that part (b) cannot be solved with the given information. Another user also chimes in, reinforcing that the EMF cannot be found without the potential difference.
distilabel_metadata.content: Evaluate the user given text extract and determine if it contains a math question and optionally and answer to this question.
  
  Output rules:
  
  1. Briefly describe the document and mention if it contains a question or a question and answer.
  2. Finalize the output with: Label: no-question,question,question-and-answer,multiple-question,multiple-question-and-answer
distilabel_metadata.role: system
distilabel_metadata.content: # Emf and Terminal Voltage
  
  nautica
  Okay here is the question:
  
  a) what is the internal resistance of a voltage source if its terminal voltage drops by 2 V when the current supplied increases by 5 A.
  
  b) Can the emf of the voltage source be found with the information supplied?
  
  I know that E = V - Ir, and I am pretty sure that a simple algebraic equation can be put together. So what formulat am I missing??
  
  Thanks
  Nautica
  
  Related Introductory Physics Homework Help News on Phys.org
  HallsofIvy
  Homework Helper
  You know that E = V - Ir so &Delta;E= &Delta;V- &Delta;I r. You are told that &Delta;E= 2volts when &Dekta;I= -5 amps. Of course, &Delta;V= 0 since the voltage source is fixed.
  Thatis: 2= -5r. Can you solve for r now? .
  
  The answer to b is NO. In effect V is the "constant of integration" when you "integrate" dE= -rdI. There is no way to find that from the information given.
  
  Last edited by a moderator:
  nautica
  I am in College Physics, we can not use calculus for an answer. So is there a reason algebraically.
  
  thanks
  nautica
  
  If u know the potential diff b/w two terminals, then u can find the emf.
  
  With this information u cannot find
  
  nautica
  So ther is no way to find emf without Potential difference???
  
  thanks
  nautica
  
  nautica
  Okay For a) here is what I got
  
  V=E-Ir
  
  or dV=dE - dIr
  
  2V = -5r
  
  so r = -.4Ohms
  
  BUT, my instructor said this was wrong b/c there I did not no the Rload and there are too many unknowns for this to be solved.
  
  I can see how part B could not be solved but this looked so simple for part a)
  
  He said this was the other equation I should have considered, but I do not see why it was needed.
  
  I = E / (Rload + r)
  
  Thanks
  nautica
distilabel_metadata.role: user
distilabel_metadata.raw_output_q_a_detector_0: The document contains a physics problem related to electromotive force (EMF) and terminal voltage. The user, nautica, asks two questions:
  
  a) What is the internal resistance of a voltage source if its terminal voltage drops by 2 V when the current supplied increases by 5 A?
  b) Can the emf of the voltage source be found with the information supplied?
  
  The user also provides their attempt at solving part (a) and mentions that their instructor indicated the solution was incorrect, suggesting the need to consider the load resistance.
  
  HallsofIvy provides a detailed response, explaining how to solve part (a) using the given formula and confirming that part (b) cannot be solved with the given information. Another user also chimes in, reinforcing that the EMF cannot be found without the potential difference.
  
  Label: question-and-answer