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Electric Charges and Fields — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsElectric Charges and Fields1 Mark
Question
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): A point charge is lying at the centre of a cube of each side. The electric flux emanating from each surface of the cube is $\frac{1^\text{th}}{6}$ of total flux.
Reason (R): According to Gauss theorem, total electric flux through a closed surface enclosing a charge is equal to $\frac{1}{\in_0}$ times the magnitude of the charge enclosed.
✓

Answer

  1. Both A and R are true, but R is not the correct explanation of A.

Explanation:

The electric flux through the cube, $\phi=\frac{\text{q}}{\in_0}.$ A cube has six faces of equal area. Therefore, electric flux through each face $=\frac{1}{6}\phi=\frac{1}{6}(\frac{\text{q}}{\in_0}).$

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