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Homework Statement
Two isolated point charges, -7 μC and +2 μC, are at a fixed distance apart. At which point is it possible for the electric field strength to be zero?
(A)......(B)...(C).....(D)
o----------------------o----------o---------------o
......-7 μC...+2 μC
I don't know how to insert image
sorry for messy drawing (I had to put little dots because it wouldn't make spaces although I spaced them out)
Homework Equations
F= k(q1)(q2)/r^2
E = F/q
The Attempt at a Solution
The actual answer is (D).
By these two equations, I got
E = kq/r^2
I thought, to make the field strength 0, I had to find the distance at which the field strength of these two charges are equal.
∴ E = E
kq/r^2 = kq/r^2
k(-7 μC )/r^2 = k(+2 μC)/r^2
I know this is way off,,, since I will cancel out the distance!
I actually did choose the right answer (D) simply because -7 μC has larger magnitude that field strength would be much smaller at (D)
Please tell me how I can solve this algebraically. Thank you :D