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Question

Physics Question on Electric Field

Two point charges +8q +8q and 2q-2q are placed as shown in the figure. The point where the electric field is zero is

A

x=lx = l

B

x=2lx = 2l

C

x=3lx = 3l

D

x=4lx = 4l

Answer

x=2lx = 2l

Explanation

Solution

Let at a point PP at a distance dd from 2q-2q charge at which the electric field is zero. E1=E2\therefore E_1 = E_2 14πε08q(l+d)2=14πε02qd2\frac{1}{4\pi\varepsilon_{0}} \frac{8q}{\left(l+d\right)^{2}} = \frac{1}{4\pi\varepsilon_{0}} \frac{2q}{d^{2}} 4d2=(l+d)24d^{2} = \left(l+d\right)^{2} 2d=l+d2d = l+d d=ld= l Hence, at x=2lx = 2l, the electric field is zero due to given charge configuration.