Ncert Exercises & Solutions

Q 1.15)

Consider a uniform electric field E = 3 × 10³ î N/C.

(a) What is the flux of this field through a square of 10 cm on a side whose plane is parallel to the y z – plane?

(b) What is the flux through the same square if the normal to its plane makes a 60 ° angle with the x-axis?

(a)

Magnitude of electric field intensity, E = 3 × 10³ N / C

Side of the square, s = 10 cm = 0.1 m

Area of the square, A = s² = 0.01 m²

The plane of the square is parallel to the y – z plane. Hence, the angle between the area vector and the electric field, θ = 0°.

Flux ( φ ) through the plane,

φ = EA cos θ

φ = 3 × 10³ × 0.01 × cos0°

φ = 30 N m ² /C

(b) Plane makes an angle of 60 ° with the x-axis.

Hence, θ = 60°

Flux, φ = EAcosθ

Flux, φ = 3 × 10 ³ × 0.01 × cos60°

Flux, φ = 30 x 0.5

Flux, φ = 15 N m ² /C