Find the electric field intensity at 10cm away from a point charge of 100 esu.
a) 1 dyne/esu
b) 10 dyne/esu
c) 100 dyne/esu
d) 9*109 dyne/esu
Explanation: We know that electric field intensity at r distance from a point charge q is defined as q/r2 in the CGS system. Here q=100 esu, r=10cm. Substituting the value we get E=1dyne/esu. We must remember that factor 1/4πε is considered only in the SI system and its value is 9*109, but in the CGS system, we simply take the value of this constant as unity.