Answer :
It's necessary that the point charge does not affect the position of the charge being tested because: C) Electric fields are inversely proportional to the square of the distance, so any change in position changes the field.
Explanation:
A point charge is used to determine the electric field around a charged particle. The space around a charged particle is called electric field. The direction of electric field is shown by electric field lines. For a point charge it is given by :
[tex]E=\dfrac{kq}{d^2}[/tex]
Where
k = electrostatic constant
q = point charge
d = distance between charges
It is clear that E is inversely proportional to the square of the distance. Hence, the correct option is (c) "Electric fields are inversely proportional to the square of the distance, so any change in position changes the field".