NEET Electric Charges and Fields — Set 8

Question 1

A charge of $ 13 \, \mu\text{C} $ is at the center of a cube of edge 50 cm. What is the flux through one face?

Accepted Answer

Total flux: $ \phi = \frac{q}{\varepsilon_0} = \frac{13 \times 10^{-6}}{8.854 \times 10^{-12}} = 1.468 \times 10^6 \, \text{Nm}^2/\text{C} $. Flux per face (6 faces): $ \phi_{\text{face}} = \frac{1.468 \times 10^6}{6} = 2.447 \times 10^5 \, \text{Nm}^2/\text{C} $.

Question 2

An infinite line charge has $ \lambda = 6 \times 10^{-6} \, \text{C/m} $. What is the electric field at 12 cm?

Accepted Answer

$ E = \frac{2 k \lambda}{r} $, $ k = 9 \times 10^9 \, \text{Nm}^2/\text{C}^2 $. $ E = \frac{2 \times 9 \times 10^9 \times 6 \times 10^{-6}}{0.12} = 9 \times 10^5 \, \text{N/C} $.

Question 3

Two charges $ +6 \, \mu\text{C} $ and $ -3 \, \mu\text{C} $ are 50 cm apart. What is the electric field magnitude at the midpoint?

Accepted Answer

Midpoint distance = 25 cm = 0.25 m. $ E_1 = 9 \times 10^9 \times \frac{6 \times 10^{-6}}{(0.25)^2} = 8.64 \times 10^5 \, \text{N/C} $ (towards $ -3 \, \mu\text{C} $). $ E_2 = 9 \times 10^9 \times \frac{3 \times 10^{-6}}{(0.25)^2} = 4.32 \times 10^5 \, \text{N/C} $ (towards $ -3 \, \mu\text{C} $). Net $ E = 8.64 \times 10^5 + 4.32 \times 10^5 = 1.296 \times 10^6 \, \text{N/C} $.

NEET Physics: Electric Charges and Fields — Practice Set 8

Q1. A charge of \( 13 \, \mu\text{C} \) is at the center of a cube of edge 50 cm. What is the flux through one face?

Q2. An infinite line charge has \( \lambda = 6 \times 10^{-6} \, \text{C/m} \). What is the electric field at 12 cm?

Q3. Two charges \( +6 \, \mu\text{C} \) and \( -3 \, \mu\text{C} \) are 50 cm apart. What is the electric field magnitude at the midpoint?

Q4. Why does the electric field inside a charged spherical shell remain zero even if the shell is irregular but closed?

Q5. A thin spherical shell of radius 6 cm has \( q = 5 \, \mu\text{C} \). What is the electric field at 8 cm from the center?

Q6. A uniform electric field \( E = 3 \times 10^3 \, \text{N/C} \) is along the y-axis. What is the flux through a square of side 60 cm in the xz-plane?

Q7. A point charge \( -8 \, \mu\text{C} \) is at the origin. What is the electric field magnitude at a point 4 m along the z-axis?

Q8. Why does the electric field strength near a charged object increase as the density of field lines increases?

Q9. A thin spherical shell of radius 5 cm has \( q = 2 \, \mu\text{C} \). What is the electric field at 3 cm from the center?

Q10. Why is the electric field inside a conductor zero when it is placed in an external electric field?