NEET Physics: Electric Charges and Fields — Practice Set 6

Q1. A uniform field \( E = 4 \times 10^3 \, \text{N/C} \) is along the z-axis. What is the flux through a rectangle of 30 cm × 20 cm in the xy-plane?

A. 220 \( \text{Nm}^2/\text{C} \)
B. 230 \( \text{Nm}^2/\text{C} \)
C. 240 \( \text{Nm}^2/\text{C} \)
D. 250 \( \text{Nm}^2/\text{C} \)

Q2. A plane sheet has \( \sigma = 2.66 \times 10^{-11} \, \text{C/m}^2 \). What is the electric field near it?

A. \( 1.2 \, \text{N/C} \)
B. \( 1.5 \, \text{N/C} \)
C. \( 1.8 \, \text{N/C} \)
D. \( 2.0 \, \text{N/C} \)

Q3. A closed surface has a net flux of \( 3.39 \times 10^5 \, \text{Nm}^2/\text{C} \). What is the charge enclosed?

A. \( 2.8 \, \mu\text{C} \)
B. \( 2.9 \, \mu\text{C} \)
C. \( 3.0 \, \mu\text{C} \)
D. \( 3.1 \, \mu\text{C} \)

Q4. A conducting sphere of radius 25 cm has an electric field of \( 2 \times 10^3 \, \text{N/C} \) at 50 cm from its center. What is the charge?

A. \( 4.0 \times 10^{-8} \, \text{C} \)
B. \( 5.0 \times 10^{-8} \, \text{C} \)
C. \( 5.2 \times 10^{-8} \, \text{C} \)
D. \( 5.56 \times 10^{-8} \, \text{C} \)

Q5. A dipole with charges \( +5 \, \mu\text{C} \) and \( -5 \, \mu\text{C} \) separated by 6 mm is in a field \( 3 \times 10^4 \, \text{N/C} \) at 30°. What is the torque?

A. \( 4.0 \times 10^{-4} \, \text{N m} \)
B. \( 4.5 \times 10^{-4} \, \text{N m} \)
C. \( 4.8 \times 10^{-4} \, \text{N m} \)
D. \( 5.0 \times 10^{-4} \, \text{N m} \)

Q6. A body gains a charge of \( -1.6 \times 10^{-7} \, \text{C} \) when rubbed. How many electrons were transferred to it?

A. \( 1 \times 10^{12} \)
B. \( 1.2 \times 10^{12} \)
C. \( 1.5 \times 10^{12} \)
D. \( 1.8 \times 10^{12} \)

Q7. A conducting sphere of radius 20 cm has a surface charge density of \( 30 \, \mu\text{C/m}^2 \). What is the total charge?

A. \( 1.2 \times 10^{-5} \, \text{C} \)
B. \( 1.4 \times 10^{-5} \, \text{C} \)
C. \( 1.51 \times 10^{-5} \, \text{C} \)
D. \( 1.6 \times 10^{-5} \, \text{C} \)

Q8. A uniform electric field \( E = 2 \times 10^3 \, \text{N/C} \) is along the z-axis. What is the flux through a rectangle of 30 cm × 50 cm in the xy-plane?

A. \( 300 \, \text{Nm}^2/\text{C} \)
B. \( 320 \, \text{Nm}^2/\text{C} \)
C. \( 350 \, \text{Nm}^2/\text{C} \)
D. \( 400 \, \text{Nm}^2/\text{C} \)

Q9. Three charges \( +3 \, \mu\text{C}, +3 \, \mu\text{C}, -6 \, \mu\text{C} \) are at the vertices of an equilateral triangle of side 2 m. What is the force on \( -6 \, \mu\text{C} \)?

A. 0.05 N
B. 0.06 N
C. 0.07 N
D. 0.08 N

Q10. A charge of \( 9 \, \mu\text{C} \) is enclosed in a cube of edge 40 cm. What is the flux through one face?

A. \( 1.5 \times 10^5 \, \text{Nm}^2/\text{C} \)
B. \( 1.69 \times 10^5 \, \text{Nm}^2/\text{C} \)
C. \( 1.8 \times 10^5 \, \text{Nm}^2/\text{C} \)
D. \( 2.0 \times 10^5 \, \text{Nm}^2/\text{C} \)

Q11. A glass rod loses \( 9.6 \times 10^{-8} \, \text{C} \) of charge when rubbed with silk. How many electrons were transferred from it?

A. \( 6 \times 10^{11} \)
B. \( 6.5 \times 10^{11} \)
C. \( 7 \times 10^{11} \)
D. \( 7.5 \times 10^{11} \)

Q12. Why does the electric field inside a uniformly charged thin spherical shell vanish, regardless of the position within it?

A. Gauss’s law
B. Coulomb’s law
C. Superposition principle
D. Charge quantization

Q13. A dipole with charges \( +4 \, \mu\text{C} \) and \( -4 \, \mu\text{C} \) separated by 8 mm is in a field \( 5 \times 10^4 \, \text{N/C} \) at 45°. What is the torque?

A. \( 1.0 \times 10^{-3} \, \text{N m} \)
B. \( 1.13 \times 10^{-3} \, \text{N m} \)
C. \( 1.2 \times 10^{-3} \, \text{N m} \)
D. \( 1.3 \times 10^{-3} \, \text{N m} \)

Q14. A thin spherical shell of radius 31 cm has \( q = 20 \, \mu\text{C} \). What is the electric field at 35 cm from the center?

A. \( 1.4 \times 10^6 \, \text{N/C} \)
B. \( 1.45 \times 10^6 \, \text{N/C} \)
C. \( 1.46 \times 10^6 \, \text{N/C} \)
D. \( 1.47 \times 10^6 \, \text{N/C} \)

Q15. A charge of \( 7 \, \mu\text{C} \) is at the center of a cube of edge 35 cm. What is the total flux through the cube?

A. \( 7.5 \times 10^5 \, \text{Nm}^2/\text{C} \)
B. \( 7.91 \times 10^5 \, \text{Nm}^2/\text{C} \)
C. \( 8.2 \times 10^5 \, \text{Nm}^2/\text{C} \)
D. \( 8.5 \times 10^5 \, \text{Nm}^2/\text{C} \)

Physics — Electric Charges and Fields

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A uniform field \( E = 4 \times 10^3 \, \text{N/C} \) is along the z-axis. What is the flux through a rectangle of 30 cm × 20 cm in the xy-plane?

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