As per this diagram a point charge `+q` is placed at the origin `O`. Work done in taking another point charge `-Q` from the point `A(0, a)` to another point `B(a, 0)` along the staight path `AB` is:

Options

A. `((-qQ)/(4pi in_(0))1/a^(2)) sqrt(2)a`
B. zero
C. `((qQ)/(4pi in_(0))1/a^(2)) 1/sqrt(2)a`
D. `((qQ)/(4pi in_(0))1/a^(2)) sqrt(2)a`

Answer

B

Explanation

Charge moves `bot^(r)` to the field lines. So the work done will be zero.