Question

A charge 4C is placed at the origin. The electric potential at a point (3,4,0) is .

• A. 4k/5
• B. 4k/3
• C. 4k/5 $\hat{i}$
• D. 4k/3 $\hat{i}$

Answer 1

The correct option is A 4k/5

The formula to find potential a point r distance away from a charge Q is $V=\frac{kQ}{r}$
But here in this question instead of giving r, we are given that the point is at (3,4,0) and charge Q=4C is at origin (0,0,0).
So to get r, we use distance formula.
$r=\sqrt{(3-0{)}^2+(4-0{)}^2+(0-0{)}^2}$
$r=\sqrt{25}$
r = 5
Now,
At (3,4,0), $V=\frac{k\times 4}{5}$
$V=\frac{4k}{5}$
And potential is a scalar, not a vector. So, it has no direction.