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NEET PHYSICSMedium

A point charge +10 \mu C is at a distance 5 cm directly above the centre of a square of side 10 cm, as shown in the figure. What is the magnitude of the electric flux through the square?

A

3.18 × 10⁵ Nm²C⁻¹

B

2.10 × 10⁵ Nm²C⁻¹

C

1.03 × 10⁵ Nm²C⁻¹

D

1.88 × 10⁵ Nm²C⁻¹

Step-by-Step Solution

To find the flux through the square, imagine the square as one face of a cube with side length 10 cm. Since the charge is 5 cm above the center of the square, it is located exactly at the center of this imaginary cube. According to Gauss's Law, the total flux through the cube is Φtotal=qε0\Phi_{\text{total}} = \frac{q}{\varepsilon_0}. Due to symmetry, the flux through one face (the square) is 16\frac{1}{6} of the total flux.

Calculation: Φsquare=16qε0\Phi_{\text{square}} = \frac{1}{6} \frac{q}{\varepsilon_0} q=10μC=10×106 Cq = 10 \mu\text{C} = 10 \times 10^{-6} \text{ C} ε0=8.854×1012 C2N1m2\varepsilon_0 = 8.854 \times 10^{-12} \text{ C}^2\text{N}^{-1}\text{m}^{-2}

Φsquare=10×1066×8.854×1012=10×10653.1241.88×105 Nm2C1\Phi_{\text{square}} = \frac{10 \times 10^{-6}}{6 \times 8.854 \times 10^{-12}} = \frac{10 \times 10^6}{53.124} \approx 1.88 \times 10^5 \text{ Nm}^2\text{C}^{-1}. (See NCERT Physics Class 12, Exercise 1.18).

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