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JEE Main 2005 (AIEEE) · Electric Field & Field Lines

Electric Field & Field Lines question from JEE Main 2005 (AIEEE)

Q51JEE Main 2005 · AIEEEMedium

Electric Field & Field Lines

Two point charges +8q+8q and −2q-2q are located at x=0x = 0 and x=Lx = L respectively. The location of a point on the xx axis at which the net electric field due to these two point charges is zero is

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Answer: (b)

  1. The null point lies beyond the smaller charge −2q-2q, at x>Lx > L.
  2. 8qx2=2q(x−L)2⇒x−Lx=12\dfrac{8q}{x^2} = \dfrac{2q}{(x-L)^2} \Rightarrow \dfrac{x-L}{x} = \dfrac{1}{2}
  3. x=2Lx = 2L
  4. So the answer is (b) 2L2L.
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