The figure shows two unequal point charges 1 q and Q, of opposite sign. Charge Q
ID: 1263806 • Letter: T
Question
The figure shows two unequal point charges 1 q and Q, of opposite sign. Charge Q has greater magnitude than charge q. In which of the regions X, Y, Z will there be a point at which the net electric field due to these two charges is zero? only region X only regions X and Z only region Z only region Y all three regions My Answers Give Up Correct Why is it that the electric field is zero only in region x? I've search the University Physics text several times and the only thing mentioned is in reference to the electric field of one particle either positive or negative vs a point charge in space. Picture would be helpful also!Explanation / Answer
There are 3 regions on the axis:
1) left of q = region X
2) between q and Q = region Y
3) right of Q = region Z
Both charges are of opposite signs and Q>q
In region Z, no such P because Q > q and the distance
In region Y, no such P because EQ and Eq have same direction.
In region X, there's such P.
When one of the charges is negative, the fields between the charges add and therefore between the charges, the field can't be zero. To the right of the Q charge the field won't be zero because Q is larger than q, even though the E field from the q will subtract from the Q field, it will not be large enough to cancel it, especially because it is decreasing by 1/(1.1+r)2 to the right of that charge. So the field will be zero to the left of the q charge (Region X).
It really doesn't matter which charge is negative. The point of zero will be the same regardless. The direction of the non-zero field will be determined by which charge is negative where the fields cancel.
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