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KCET2020PhysicsElectrostatics

A point charge q is placed at the corner of a cube of side a as shown in the figure. What is the electric flux through the face A B C D ?

Options

  1. A0
  2. Bq 24 ₀
  3. Cq 6 ₀
  4. Dq 72 ₀

Correct answer

B. q 24 ₀

Step-by-step solution

If charge is placed at the one corner of a cube, then it can be shared further by 8 cubes. Charge on one cube = q 8 Now, in any given cube this charge will be touching 3 out of 9 of cube faces. So, the area vector of that side and the electric field vector will be perpendicular. So, flux through those 3 sides will be zero. However, equal amount of flux will flow from other 3 sides. So, flux through one side = ( q / 8 3 ) 1 ₀ = q 24 ₀ Hence, flux through one face (A B C D)= q 24 ₀

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