Two point charges\[+8q\]and\[-2q\]are located at\[x=0\]and\[x=L\]respectively. The location of a point on the x-axis at which the net electric field due to these two point charges is zero, is
AIEEE Solved Paper-2005
A)2L
B) L/4
C) 8L
D) 4L
Correct Answer:
A
Solution :
Suppose that a point B, where net electric field is zero due to charges 8 q and The electric field at B due charge 8 q at O, and the electric field at B due to charge -2q at A, According to condition, \[\frac{1}{4\pi {{\varepsilon }_{0}}}\,\frac{8q}{{{a}^{2}}}\,=\frac{1}{4\pi {{\varepsilon }_{0}}}\,\frac{2q}{{{(a+L)}^{2}}}\] Thus, at distance 2L from origin, net electric field will be zero.