Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Internal resistance proportional to current?

  1. Apr 3, 2015 #1

    CAH

    User Avatar

    The terminal voltage and current are measured as the resistance is decresed through a cell with emf and internal resistance. Graph of V (y axis) I (x axis) shows straight line decreasing gradient.
    1. Explain why terminal pd decreases as the current increases.

    is terminal pd the same as pd/voltage? I thought the pd across a resistor would always be the same provided your not adding resistors. However the mark scheme says:

    mention of pd across internal resistance or loss in internal resistance or emf>V,
    pd across internal resistance/loss volts increases with current or correct use of equation to demonstrate

    So does the internal resistance increase with the current and so voltage is lost through wires?

    Thanks :smile:
     
  2. jcsd
  3. Apr 3, 2015 #2

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    No. As with all resistances, the voltage dropped across it is proportional to the current and the internal resistance is usually assumed to be constant. That is a bit of an oversimplification for many components, though.
     
  4. Apr 3, 2015 #3

    CAH

    User Avatar

    so the voltage will continuously drop to internal resistance? It seems like a lot of volts lost just to internal resistance?
     
  5. Apr 3, 2015 #4

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    IF the internal resistance is 1 Ohm then every Amp will cause a drop of 1 Volt. There's no surprise there.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Internal resistance proportional to current?
  1. Internal resistance (Replies: 1)

  2. Resistance and Current (Replies: 23)

Loading...