Goal: Reason regarding electric fields
Source: 283 –

Charge, Q, is at the origin. Points A-E are positions where other
charges may be present. Etotal at point F is non-zero and
points in the +i direction. Which of the following situations
could account for this?
- Another charge is present at position
A.- Two other charges are present at C & D.
- Two other
charges are present at D & B.- Two other charges are present at
E & A.
- A only
- B only
- C only
- D only
- A and B
- A, C and D
- A, B, and D
- A, B, C, and D
Commentary:
Answer
(2) Only a charge at C can counter the y component of the field of Q at
F. A charge at B or D can then create a field at F that points in the i
direction.