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There exists an electric field of 1 N/C along the Y direction. The flux passing through a square of side 1 m placed in the XY plane inside the electric field is ________.

Asked in GUJCET 2011 · Electric flux through a surface

• (1) 1.0 N m² C⁻¹
• (2) 10.0 N m² C⁻¹
• (3) 2.0 N m² C⁻¹
• (4) zero

Step-by-step solution

Why the other options are wrong

• (1) Uses φ=EA and forgets the angle. A square in the XY plane has its normal along Z, perpendicular to the field along Y, so cos θ=0.
• (2) No single slip gives 10.0: with E=1 N/C and A=1 m² the flux can be at most 1.0, and here it is zero because the field lies in the plane of the square.
• (3) No single slip gives 2.0; it would need the field normal to the square and both faces counted. Here the field lies in the square's plane, so no flux crosses it at all.

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