Class-12th Physics, CBSE and UP Board
Electric Charges and Fields,
Chapter-1, Exercise -1, Q-1.18
NCERT Solutions for Class 12th Physics
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.)
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Refer Figure 1.34 Exercise 1.18
The square can be considered as one face of a cube of edge 10 cm with a centre where charge q is placed. According to Gauss’s theorem for a cube, total electric flux through all its six faces.
ΦTotal = q/ε0
Hence, electric flux through one face of the cube i.e., through the square is
Φ=ΦTotal /6 =1/6 x q/ε0
Where,
ε0 = Permittivity of free space = 8.854 x 10–12 N–1C2 m-2
q = 10 µ C = 10 x 10-6 C
Therefore Φ=1/6 x (10 x 10-6)/ 8.854 x 10-12
= 1.88 x 105 N m2 C-1
Therefore, electric flux through the square is 1.88 x 105 N m2 C-1