1. Limited time only! Sign up for a free 30min personal 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!

Direction of electric field lines

  1. May 1, 2010 #1
    I have an intuitive understanding of electric fields but when it comes to defining it on a test I wouldn't know what to say. Is the electric field defined as the force produced by a charged object on a positive test charge or any other charged object? Also if you were told to draw the electric field lines emanating from a charged object on its own (as opposed to acting on another charged object) would you just assume its in relation to a positive test i.e. lines pointing outward for a positively charged object lines pointing inward for a negatively charged object.
  2. jcsd
  3. May 2, 2010 #2


    User Avatar
    Science Advisor
    Gold Member

    There is probably a more official, technical answer, but I would just say that the electric field is the vector force acting on a positive test charge. The Lorentz force for the electric field is simply qE (where E is a vector). So the field will point in the same direction as the force for positive charge. The value of your test charge is going to be dictated by your units. For example, we could just come up with a sytem of units so that the electric field has units of N/C. Thus, we would use a test charge of 1 C (or any positive charge in C but you divide the measured source by the charge's value) and directly get the electric field by measuring the force in Newtons.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook