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JEE Main 2024 (8 Apr, Shift 2) · Electric Field & Field Lines

Electric Field & Field Lines question from JEE Main 2024 (8 Apr, Shift 2)

Q18JEE Main 2024 · 8 APR · SHIFT 2Medium

Electric Field & Field Lines

If the net electric field at point PP along YY axis is zero, then the ratio of ∣q2q3∣\left|\frac{q_2}{q_3}\right| is 85x\frac{8}{5\sqrt{x}}, where x=x = ________.

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Answer: 5

  1. Distances: r2=22+42=20r_2 = \sqrt{2^2 + 4^2} = \sqrt{20} cm, r3=32+42=5r_3 = \sqrt{3^2 + 4^2} = 5 cm.
  2. The yy-component of +q2+q_2's field (upward) must cancel that of −q3-q_3's field (downward).
  3. kq220⋅420=kq325⋅45\dfrac{kq_2}{20}\cdot\dfrac{4}{\sqrt{20}} = \dfrac{kq_3}{25}\cdot\dfrac{4}{5}
  4. q2q3=2020125=8525=855\dfrac{q_2}{q_3} = \dfrac{20\sqrt{20}}{125} = \dfrac{8\sqrt{5}}{25} = \dfrac{8}{5\sqrt{5}}
  5. So x=5x = 5.
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