1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simple question about potential

  1. Jul 6, 2016 #1
    1. The problem statement, all variables and given/known data
    photo:
    http://s613.photobucket.com/user/Yan_Wa_Chung/media/02_zpsbdlufj1e.png.html

    2. Relevant equations
    potential = kq1q2 / r

    3. The attempt at a solution
    The answer is D. Which states "The electric potential in P is higher than Q" is correct. But my answer is B. By right hand rule, the current goes from Q to P. The formula of potential has a positive sign. So I think Q has a higher potential as work is needed to move the protons from P to Q. Why am I wrong?
     
  2. jcsd
  3. Jul 6, 2016 #2

    cnh1995

    User Avatar
    Homework Helper

    Your right hand rule analysis correct but P is at a higher potential than Q. The conductor in the magnetic field is acting as a source. You can replace it with a battery. What is the direction of current inside a voltage source when it is delivering power?
     
  4. Jul 6, 2016 #3
    Do you mean placing a battery in QP, then I get P is the positive terminal and Q is the negative terminal, so P has a higher potential . Thanks for reminding me the source is in the magnetic field.
     
  5. Jul 6, 2016 #4

    cnh1995

    User Avatar
    Homework Helper

    Yes. When a voltage source is delivering power, current flows from -ve to +ve terminal inside the source.
     
  6. Jul 6, 2016 #5
    is positive terminal always have a higher potential even when a voltage source is delivering power?
     
  7. Jul 6, 2016 #6

    cnh1995

    User Avatar
    Homework Helper

    Conventionally, +ve terminal is always at a higher potential than the -ve terminal (of the same source), irrespective of the power flow. If the current is flowing from +ve terminal to -ve terminal inside the component, it is absorbing power and if the current is flowing from -ve to +ve terminal inside the component, the component is acting as a source of power. Note that the current here is the conventional current. So, for a power delivering voltage source, current flows from -ve to +ve terminal inside the source and for a power absorbing voltage source, current flows from +ve to -ve terminal inside the source.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Simple question about potential
Loading...