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Electric Charges And Fields

Question

Define electric flux. Is it a scalar or a vector quantity?
A point charge q is at a distance of d/2 directly above the centre of a square of side d, as shown in the figure. Use Gauss’ law to obtain the expression for the electric flux through the square.
b) If the point charge is now moved to a distance 'd' from the centre of the square and the side of the square is doubled, explain how the electric flux will be affected.

Solution

The total number of electric field lines crossing an area placed normal to the electric field is termed as electric flux.

It is denoted by Φ.

$ϕ_{E} = \vec{E} . \vec{ds}$

Electric flux is a scalar quantity, its SI unit is Nm²C^-1

Electric flux through square is

$ϕ_{E} = \frac{q}{ε_{0} 6}$

b) Flux will not be changed,

i.e., $ϕ_{E} = \frac{q}{ε_{0} 6}$