Question

A charge of -16 nC is placed a distance L to the right of a charge of +6 nC.  One wants to place a point charge in vicinity of these two charges so that the net force on it is zero.  

1. If you put the third charge between the two charges the net electrostatic force on it

1. Can be zero
2. Cannot be zero
3. Whether one chooses a or b depends on the sign of the third charge

2. If you put the third charge to the left of the positive charge  the net electrostatic force on it

1. Can be zero
2. Cannot be zero
3. Whether one chooses a or b depends on the sign of the third charge

3. If you put the third charge to the right of the negative  charge  the net electrostatic force on it  

1. Can be zero
2. Cannot be zero
3. Whether one chooses a or b depends on the sign of the third charge

Please explain each answer and how you got them, as I do not understand the concept thoroughly. Thank you!!

Answer 1