Question

Two point charges +Q and -2Q are separated by a distance d on the X-axis. If a third point charge is placed in the two charges’ plane,

A) Where would the third charge be placed to experience a zero net force from the two point charges?

B) Is the third charge must be positive or negative?

Answer 1

Solution

A) The third charge must be placed on the line connecting the two charges but not on in between the charges but on the other side of charge +Q . It must be also placed at a distance from charge +Q given by,

B) It can be either positive or Negative. Both of them will experience zero force. This is due to the fact that, the electric force on a charge is given by,

Where q is the charge placed at that point and E is the electric field at that point. Since q cannot be zero which makes no sense. But if E is zero there then whatever the charge q placed, the force will be always zero. Thus here at the point given in A) the field E will be zero and hence whatever the charged placed at that point,the force on it will be zero.

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