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!

Homework Help: Electric field direction and hovering charged object

  1. Sep 2, 2010 #1
    1. The problem statement, all variables and given/known data

    A small object of mass 3.64 g and charge -18.1 µC is suspended motionless above the ground when immersed in a uniform electric field perpendicular to the ground. What are the magnitude and direction of the electric field?


    2. Relevant equations

    E=F/q

    3. The attempt at a solution

    I solved for the magnitude and was fine with that but was wondering why the electric field direction would be downwards?

    Why couldn't it be upwards?

    E = m*g / -q = -#

    My logic was that a - electric field upwards would make the charged object hover since - and - repel.

    I guess if it was going downwards the same effect would still occur, but I don't understand (if this is even right...) how to determine if up or down.
    Am i completely off track on how to think about this?
     
  2. jcsd
  3. Sep 2, 2010 #2
    The direction of the force depends on the electric field and the sign of the charge. Positive charges experience a force in the direction of the electric field, and negative charges experience a force in the opposite direction.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook