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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumApplication

JEE Main 24 February 2021, Shift 1, Physics Q15

Question 15 of 90 in this shift, Physics question 15 of 30, Section A.

A cube of side ‘a’ has point charges +Q located at each of its vertices except at the origin where the charge is −-Q. The electric field at the centre of cube is :

The figure, in words

A cube drawn in perspective with axes: x pointing up, z pointing right, y pointing towards the lower left. Seven vertices are labelled +Q and the vertex at the origin (where the axes meet, bottom back corner) is labelled −Q. An edge at the bottom front is marked with length a.
  1. (1)−Q33πε0a2(x^+y^+z^)\frac{-Q}{3\sqrt{3}\pi\varepsilon_0 a^{2}}\left(\hat{x}+\hat{y}+\hat{z}\right)
  2. (2)Q33πε0a2(x^+y^+z^)\frac{Q}{3\sqrt{3}\pi\varepsilon_0 a^{2}}\left(\hat{x}+\hat{y}+\hat{z}\right)
  3. (3)−2Q33πε0a2(x^+y^+z^)\frac{-2Q}{3\sqrt{3}\pi\varepsilon_0 a^{2}}\left(\hat{x}+\hat{y}+\hat{z}\right)Official answer
  4. (4)2Q33πε0a2(x^+y^+z^)\frac{2Q}{3\sqrt{3}\pi\varepsilon_0 a^{2}}\left(\hat{x}+\hat{y}+\hat{z}\right)

Official answer

Option 3

NTA final key.

Chapter
Electric Charges and Fields
Topic
Electric Field
Idea tested
Missing Charge Superposition Trick

Same topic in other shifts

All Electric Field questions
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  4. 2 Apr 2025, Shift 1 · Q37Consider two infinitely large plane parallel conducting plates as shown below. The plates are uniformly charged with a surface charge…EasySingle correctHas a figure
  5. 2 Apr 2025, Shift 1 · Q39A point charge +q+q is placed at the origin. A second point charge +9q+9q is placed at (d,0,0)(d, 0, 0) in Cartesian coordinate system. The…EasySingle correct
  6. 2 Apr 2025, Shift 2 · Q44Consider a circular loop that is uniformly charged and has a radius a2a\sqrt{2}. Find the position along the positive zz-axis of the…MediumSingle correct

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 108 of the 174 JEE Main shifts held from 2017 to 2026.