4. Two 1 Coulomb charges are kept at 1m distance in air medium. Force of attraction or repulsion between them will be ________ a) 9*109 N b) 1 dyne c) 1 N d) 3*103 N
Answer: a Explanation: According to Coulomb’s Law, F=14πεo∗q1q2r2. And 14πεo = 9*109N in the SI system. In this case, q1=q2=1C and r=1m. Now substituting the values we get F=9*109N. Similarly, the electric field at a distance of 1m from a 1C charge is 9*109N/C.
