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Question:

The electric field in a region of space is given by E = E₀î + 2E₀ĵ where E₀ = 100 N/C. The flux of this field through a circular surface of radius 0.02m parallel to the Y-Z plane is nearly:

0.02Nm²/C

3.14Nm²/C

0.005Nm²/C

0.125Nm²/C

Solution:

Answer is A.
We know that, Φ = E.A Cos θ. Since the surface area is parallel to the Y-Z plane, therefore, the y component of the electric field will not contribute to the flux through the circular surface.
So, Φ = πr²E₀ = 3.14 × 0.0004 × 100 = 0.125 Nm²/C