Question

In Coulomb's law, the constant of proportionality K has the units $N{m}^2/C^2$ then the magnitude of K in air is :

• A. $9\times {10}^5$
• B. $9\times {10}^9$
• C. $9\times {10}^3$
• D. none of these

Answer 1

Answer: (B)

$9\times {10}^9$

In Coulomb's law, the value of constant proportionality is $K=\frac{1}{4\pi {ϵ}_0}=\frac{1}{4\times 3.14\times (8.85\times {10}^{-12})}=8.99\times {10}^9\sim 9\times {10}^{9}N{m}^2/C^2$