An electric field is measured at 3.00×105 N/C at a distance from a source point charge of 3.00×10−6 C. How far is the point from the source charge?

0.09 m
0.30 m
0.36 m
0.60 m

Question

An electric field is measured at 3.00×105 N/C at a distance from a source point charge of 3.00×10−6 C. How far is the point from the source charge?

0.09 m
 0.30 m
 0.36 m
 0.60 m

jennylove · Answer

im not sure where to begin :/

justjm · Answer

You must use the formula

$E=k\frac{Q}{r^2}$
where k=Coulomb's constant
E=Electric field in N/C
Q=Point charge in C
r=radius in m
 
Plugging in the values

$3.00\times10^5~\text{N/C}=k\frac{3.00\times10^{-6}}{r^2}$

You can use algebra to isolate r

justjm · Answer

Did you understand it yet?

for 'k' you might need to get that online or on your calculator