Hello students, so first of all we understand, what is the electric flux?

Electric flux measures how much the electric field ‘flows’ through an area.

Or we can say that Electric flux over an area in an electric field is a measure of the total number of electric field lines crossing a surface.

Mathematically, we can calculate the electric flux passing through an area by the dot product of electric field vector and area vector.

**ϕ = E·S = EScosθ**

where θ is the angle between electric field E and outward normal to the area element.

**👉** Electric flux **ϕ** will be maximum when cosθ is max = 1, i.e.,**θ = 0°**, i.e., electric field is normal to the area.

Electric flux **ϕ** will be minimum when cosθ is min = 0, i.e., **θ = 90°**, i.e. field is parallel to the area.

For an irregular surface the electric flux can be calculated as

**👉** For a closed surface the flux comes outside to the surface is taken positive (because θ < 90°) and the flux going inside to the surface is taken negative (because θ > 90°).

**👉** Electric flux is a **scalar **quantity.**👉** **SI unit** of Electric flus is **V-m** or **N-m2/C.** Dimensions : **[ML ^{3} T^{-3} A^{-1} ]**

**The value of electric flux is zero in the following cases:**

(a) If a dipole is (or many dipoles are) enclosed by a closed surface.

(b) Magnitude of (+ve) and (-ve) charges are equal inside a closed surface.

(c) If no charge is enclosed by the closed surface.

(d) Incoming flux (- ve) = out going flux (+ve)

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**✅Sharpen Your Pencil ✍️**

**Q. 1. A rectangular surface of sides 10 cm and 15 cm is placed inside a uniform electric field of 25 N/C, such that normal to the surface makes an angle of 60° with the direction of electric field. Find the flux of electric field through the rectangular surface.**

**Q. 2. Electric flux over a surface in an electric field may be**

(a) positive (b) negative

(c) zero (d) All of the above

**🔻Comment the Answer💬**

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