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NEET PHYSICSELECTRIC CHARGES AND FIELDSEasy

Question

A surface of side L metre in the plane of the paper is placed in a uniform electric field E (volt/m) acting along the same plane at an angle \theta with the horizontal side of the square as shown in figure. The electric flux linked to the surface in unit of V-m, is

A

EL²

B

EL² cos \theta

C

EL² sin \theta

D

0

Step-by-Step Solution

Electric flux ΦE\Phi_E is defined as the scalar product of the electric field vector E\mathbf{E} and the area vector A\mathbf{A}: ΦE=EA=EAcosα\Phi_E = \mathbf{E} \cdot \mathbf{A} = EA \cos \alpha

Where α\alpha is the angle between the electric field lines and the normal (perpendicular) to the surface area , .

  1. Direction of Area Vector (mathbfA\,mathbf{A}): The square surface lies in the plane of the paper. By definition, the area vector is always perpendicular to the surface. Therefore, A\mathbf{A} is perpendicular to the plane of the paper .
  2. Direction of Electric Field (mathbfE\,mathbf{E}): The problem states that the electric field acts along the same plane (the plane of the paper).
  3. Angle α\alpha: Since the area vector is perpendicular to the paper and the electric field is parallel to the paper, the angle between them is 9090^\circ (π/2\pi/2).

Substituting this into the flux formula: ΦE=EAcos(90)=EA(0)=0\Phi_E = EA \cos(90^\circ) = EA(0) = 0.

Physically, this means the electric field lines graze the surface parallel to it and do not penetrate through it, resulting in zero flux. The angle θ\theta given in the problem (between E\mathbf{E} and the side of the square) is irrelevant to the flux calculation in this orientation.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from ELECTRIC CHARGES AND FIELDS. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSELECTRIC CHARGES AND FIELDSsurfaceplaceduniformelectricacting

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