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Defining Electric Field around a charge

  1. May 14, 2013 #1
    Electric field around a charge or system of charges is defined as the force experienced per unit charge. Won't the original field be disturbed by the test charge's own field ? How then the original field be measured accurately ?
  2. jcsd
  3. May 14, 2013 #2
    Hmm...How do I way this? Force and field are related concepts but not entirely the same thing.

    First of all you would be right to say that the field in some space would be altered if you introduce a test charge or any charge for that matter into the "picture" and if I throw in another charge into the space, the field will change as a result. However when you measure a field, what you are essentially doing is probing the force per unit charge that your test charge experiences due solely to the contribution of the other charges in the system. You must remember that the an object cannot exert a force on itself .

    I'm terrible at explaining stuff but hope this helps!
    Last edited: May 14, 2013
  4. May 14, 2013 #3


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    Staff: Mentor

    ...in the limit as the magnitude of the test charge approaches zero.
  5. May 31, 2013 #4
    Yes, the original field will be disturbed by the test charge's own field.
    It is considered that the value of the test charge taken is very low i.e. the minimum value of the test charge is taken so that the disturbance in the original field is minimum and this minimum disturbance can be neglected.
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