Question

What is the electric potential of a 2.2 µC charge at a distance of 6.3 m from the charge? Recall that Coulomb’s constant is k = 8.99 × 109 N • ___ V
What is the electric potential at a distance of 99 m from the charge?___ V

Answer 1

1) The electric potential at a distance r from a single point charge is given by
$V(r) = k \frac{q}{r}$
where k is the Coulomb's constant, q is the charge and r is the distance from the charge.

The charge in this problem is
$q=2.2 \mu C =2.2 \cdot 10^{-6} C$
So the potential at distance $r=6.3 m$ is
$V=k \frac{q}{r}=(8.99 \cdot 10^9 Nm^2 C^{-2}) \frac{2.2 \cdot 10^{-6} C}{6.3 m}=3139 V$

2) By using the same formula as before, we can find the electric potential at distance r=99 m from the charge:
$V=k \frac{q}{r}=(8.99 \cdot 10^9 Nm^2C^{-2}) \frac{2.2 \cdot 10^{-6} C}{99 m}=198 V$

Answer 2

According to Edge, the answers is 

3100 V

and 

200v