Posted by **Robert** on Tuesday, August 14, 2012 at 11:55pm.

A charge +q is at the origin. A charge –2q is at x = 2.00 m on the x axis. For what finite value(s) of x is (a) the electric field zero? (b) the electric potential zero?

- Physics - Electromagnetism -
**Elena**, Wednesday, August 15, 2012 at 8:43am
Let the point where E=0 be to the left from the charge q and separated by distance “x” from q and by distance (2+x) from -2q. Then

kq/x²=k2q/(2+x)²,

x²-4x-4 = 0

x= 2±√(4-4) =2.

The point where E=0 is x= - 2m.

Let the point where φ=0 be to the right from q and separated by distance x from it.

kq/x =k2q/(2-x),

x=2/3 m

The point where φ =0 is x=+ 2/3 m.

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