Question

Question 1.18: A point charge +10 μC is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)

Class 12 - Physics - Electric Charges And Fields Electric Charges And Fields Page-47

Answer 1

Let's assume that given square be one face of the cube of edge is 10cm .

as charge on +10microC is at a distance of 5xm above the centre of square so, it is enclosed by the cube .
hence by Gauss ' s theorem, electric flux linked with the cube is flux = q/ε₀
= 10 × 10^-6/8.85 × 10^-12
= 1.13 × 10^6 Nm²/C

so, the magnitude of the electric flux through the square is $\bf{\phi_{sq}=\frac{\phi}{6}}$
= 1.13/6 × 10^6 = 1.9 × 10^5 Nm²/C

Answer 2

Ф = q/∈o

Ф total = Ф/6

           = 1/6 × q/∈o

            = 10*10^-6/6*8.85*10^-12

             = 1.88*10^5 Nm²/C