Multiple choice (show your work if any):

Question

1) Two point charges q1=-10^-5 C and q2=-9×10^-5 C are placed respectively at two points A and B 40 cm apart. The electric field is null at a point C of [AB] such that :

a) AC=50cm b) AC=10cm c) AC=20cm d) point C doesn't exist

2) Same given. The electric field is null at a point C outside [AB] such that :

a) AC=50cm b) AC=30cm c) AC=20cm d) point C does not exist

Answer 1

E1 = kq1/r^2
same for E2
where do vectors cancel?