# Two 1 Coulomb charges are kept at 1m distance in air medium.

Two 1 Coulomb charges are kept at 1m distance in air medium. Force of attraction or repulsion between them will be ________

A. 9*10^9 N

B. 1 dyne

C. 1 N

D. 3*10^3 N

The question was asked by my college professor while I was bunking the class.

My doubt stems from Coulomb’s Law in section Charges and Fields of Physics – Class 12

Right option is A. 9*10^9 N

The best explanation: According to Coulomb’s Law, F=$$\frac {1}{4\pi \varepsilon_o }*\frac {q_1q_2}{r^2}$$. And $$\frac {1}{4\pi \varepsilon_o}$$ = 9*10^9N in the SI system. In this case, q1=q2=1C and r=1m. Now substituting the values we get F=9*10^9N. Similarly, the electric field at a distance of 1m from a 1C charge is 9*10^9N/C.