Question

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

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

Answer 1

The correct option is A $\frac{4k}{5}$

So what is the formula to find potential a point r distance away from a charge Q?
$V=\frac{kQ}{r}$
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 there can be no along with it.