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Friday, 9 October

JEE Main 2020 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 8 January 2020, Shift 1, Physics Q10

Question 10 of 75 in this shift, Physics question 10 of 25, Section A.

Three charged particles A, B and C with charges −4q-4q, 2q2q and −2q-2q are present on the circumference of a circle of radius d. The charged particles A, C and centre O of the circle formed an equilateral triangle as shown in figure. Electric field at O along x-direction is :

The figure, in words

Circle of radius d centred at O with x and y axes. A (-4q) in the first quadrant at 30 degrees above +x axis, C (-2q) in the fourth quadrant at 30 degrees below +x axis, B (2q) in the second quadrant with angle 150 degrees marked from OA to OB (B lies on the extension of line CO beyond O). OA = OB = OC = d.
  1. (1)3q4πϵ0d2\frac{\sqrt{3}q}{4\pi\epsilon_0 d^2}
  2. (2)33q4πϵ0d2\frac{3\sqrt{3}q}{4\pi\epsilon_0 d^2}
  3. (3)23qπϵ0d2\frac{2\sqrt{3}q}{\pi\epsilon_0 d^2}
  4. (4)3qπϵ0d2\frac{\sqrt{3}q}{\pi\epsilon_0 d^2}Official answer

Official answer

Option 4

NTA final key (Jan 2020).

Chapter
Electric Charges and Fields
Topic
Electric Field
Idea tested
Superposition Principle for Electric Fields

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.