# Given a Uniform Electric Field → E = 2 × 10 3 ^ I N/C, Find the Flux of this Field Through a Square of Side 20 Cm, Whose Plane is Parallel to the Y−Z Plane. - Physics

Given a uniform electric field $\vec{E} = 2 \times {10}^3 \ \hat{i}$  N/C, find the flux of this field through a square of side 20 cm, whose plane is parallel to the y−z plane. What would be the flux through the same square, if the plane makes an angle of 30° with the x−axis ?

#### Solution

When the plane is parallel to the y-z plane:

$\phi = \vec{E .} A^\rightharpoonup$

$Here:$

$\vec{E} = 2 \times {10}^3 \ \hat{i} N/C$

$A^\rightharpoonup = \left( 20 cm \right)^2 \hat{i} = 4 \times {10}^{- 2} \ \hat{i} m^2$

$\therefore \phi = \left( 2 \times {10}^3 \ \hat{i} \right) . \left( 4 \times {10}^{- 2} \ \hat{i} \right)$

$\Rightarrow \phi = 80 \ \text { Weber }$

When the plane makes a 30° angle with the x-axis, the area vector makes a 60° angle with the x-axis.

$\phi = \vec{E .} A^\rightharpoonup$

$\Rightarrow \phi = EA \cos\theta$

$\Rightarrow \phi = \left( 2 \times {10}^3 \right)\left( 4 \times {10}^{- 2} \right)\cos60°$

$\Rightarrow \phi = \frac{80}{2}$

$\Rightarrow \phi = 40 \text { Weber}$

Concept: Electric Flux
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