NEET Physics: Electric Charges and Fields — Practice Set 4

Q1. How many electrons must be added to a neutral body to give it a charge of \( -8 \times 10^{-8} \, \text{C} \)?

A. \( 4 \times 10^{11} \)
B. \( 5 \times 10^{11} \)
C. \( 6 \times 10^{11} \)
D. \( 7 \times 10^{11} \)

Q2. A conducting sphere of radius 14 cm has an electric field of \( 7 \times 10^3 \, \text{N/C} \) at 28 cm from its center. What is the charge?

A. \( 5.8 \times 10^{-8} \, \text{C} \)
B. \( 5.9 \times 10^{-8} \, \text{C} \)
C. \( 6.0 \times 10^{-8} \, \text{C} \)
D. \( 6.1 \times 10^{-8} \, \text{C} \)

Q3. A dipole with charges \( +2 \, \mu\text{C} \) and \( -2 \, \mu\text{C} \) separated by 1 mm is in a field of \( 6 \times 10^4 \, \text{N/C} \) at 90°. What is the torque?

A. \( 1.0 \times 10^{-4} \, \text{N m} \)
B. \( 1.2 \times 10^{-4} \, \text{N m} \)
C. \( 1.5 \times 10^{-4} \, \text{N m} \)
D. \( 1.8 \times 10^{-4} \, \text{N m} \)

Q4. A uniform field \( E = 5 \times 10^3 \, \text{N/C} \) is along the x-axis. What is the net flux through a cube of side 30 cm with faces parallel to coordinate planes?

A. \( 0 \, \text{Nm}^2/\text{C} \)
B. \( 450 \, \text{Nm}^2/\text{C} \)
C. \( 900 \, \text{Nm}^2/\text{C} \)
D. \( 1350 \, \text{Nm}^2/\text{C} \)

Q5. A plane sheet has \( \sigma = 5.31 \times 10^{-11} \, \text{C/m}^2 \). What is the electric field near it?

A. \( 2.5 \, \text{N/C} \)
B. \( 3.0 \, \text{N/C} \)
C. \( 3.5 \, \text{N/C} \)
D. \( 4.0 \, \text{N/C} \)

Q6. Three charges \( +7 \, \mu\text{C}, -5 \, \mu\text{C}, +3 \, \mu\text{C} \) are at the vertices of an equilateral triangle of side 2 m. What is the force magnitude on \( +7 \, \mu\text{C} \)?

A. 0.09 N
B. 0.095 N
C. 0.098 N
D. 0.10 N

Q7. A thin spherical shell of radius 30 cm has a charge of \( 18 \, \mu\text{C} \). What is the electric field at a point 36 cm from the center?

A. \( 1.25 \times 10^6 \, \text{N/C} \)
B. \( 1.3 \times 10^6 \, \text{N/C} \)
C. \( 1.4 \times 10^6 \, \text{N/C} \)
D. \( 1.5 \times 10^6 \, \text{N/C} \)

Q8. A charge of \( 5 \, \mu\text{C} \) is enclosed in a cube of edge 30 cm. What is the flux through one face?

A. \( 9.0 \times 10^4 \, \text{Nm}^2/\text{C} \)
B. \( 9.42 \times 10^4 \, \text{Nm}^2/\text{C} \)
C. \( 9.8 \times 10^4 \, \text{Nm}^2/\text{C} \)
D. \( 1.0 \times 10^5 \, \text{Nm}^2/\text{C} \)

Q9. An infinite line charge has a linear charge density \( \lambda = 2 \times 10^{-6} \, \text{C/m} \). What is the electric field at 5 cm from the wire?

A. \( 5.4 \times 10^5 \, \text{N/C} \)
B. \( 7.2 \times 10^5 \, \text{N/C} \)
C. \( 9.0 \times 10^5 \, \text{N/C} \)
D. \( 1.08 \times 10^6 \, \text{N/C} \)

Q10. Why does the electric field inside a charged insulator depend on the distribution of charges within it?

A. Charge quantization
B. Field symmetry
C. Charge mobility
D. Charge distribution

Q11. A uniform field \( E = 8 \times 10^3 \, \text{N/C} \) is along the y-axis. What is the flux through a circle of radius 15 cm in the xz-plane at 30° to the y-axis?

A. 450 \( \text{Nm}^2/\text{C} \)
B. 470 \( \text{Nm}^2/\text{C} \)
C. 490 \( \text{Nm}^2/\text{C} \)
D. 510 \( \text{Nm}^2/\text{C} \)

Q12. What fundamental concept explains why the electric field just outside a charged conductor is perpendicular to its surface?

A. Charge quantization
B. Field symmetry
C. Electrostatic equilibrium
D. Superposition principle

Q13. A charge of \( -2 \, \mu\text{C} \) produces a flux of \( -2.26 \times 10^5 \, \text{Nm}^2/\text{C} \) through a spherical surface. What is the radius of the surface?

A. 10 cm
B. 20 cm
C. Flux is independent of radius
D. 50 cm

Q14. Two charges \( +5 \, \mu\text{C} \) and \( -5 \, \mu\text{C} \) are 30 cm apart. What is the potential energy of the system?

A. \( -0.9 \, \text{J} \)
B. \( -0.75 \, \text{J} \)
C. \( -0.6 \, \text{J} \)
D. \( 0.75 \, \text{J} \)

Q15. A thin spherical shell of radius 11 cm has \( q = 5 \, \mu\text{C} \). What is the electric field at 9 cm from the center?

A. \( 1.2 \times 10^6 \, \text{N/C} \)
B. \( 1.0 \times 10^6 \, \text{N/C} \)
C. \( 0 \, \text{N/C} \)
D. \( 0.8 \times 10^6 \, \text{N/C} \)

Physics — Electric Charges and Fields

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How many electrons must be added to a neutral body to give it a charge of \( -8 \times 10^{-8} \, \text{C} \)?

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