NEET Electric Charges and Fields — Set 9

Question 1

A thin spherical shell of radius 8 cm has $ q = 4 \, \mu\text{C} $. What is the electric field at 6 cm from the center?

Accepted Answer

Inside shell ($ r < R $): $ E = 0 $ (Gauss’s law).

Question 2

What ensures that the electric field lines from a negative charge always terminate on it rather than extend to infinity?

Accepted Answer

Negative charges attract positive test charges, so field lines, representing the force direction on a positive charge, point inward toward the negative charge. This attraction defines their termination, unlike positive charges where lines extend outward.

Question 3

A thin spherical shell of radius 12 cm has a total charge of $ 9 \, \mu\text{C} $. What is the electric field at 15 cm from the center?

Accepted Answer

Outside shell ($ r > R $): $ E = \frac{k q}{r^2} $. $ k = 9 \times 10^9 \, \text{Nm}^2/\text{C}^2 $, $ q = 9 \times 10^{-6} \, \text{C} $, $ r = 0.15 \, \text{m} $. $ E = 9 \times 10^9 \times \frac{9 \times 10^{-6}}{(0.15)^2} = 9 \times 10^9 \times \frac{9 \times 10^{-6}}{0.0225} = 3.6 \times 10^6 \, \text{N/C} $.

NEET Physics: Electric Charges and Fields — Practice Set 9

Q1. A thin spherical shell of radius 8 cm has \( q = 4 \, \mu\text{C} \). What is the electric field at 6 cm from the center?

Q2. What ensures that the electric field lines from a negative charge always terminate on it rather than extend to infinity?

Q3. A thin spherical shell of radius 12 cm has a total charge of \( 9 \, \mu\text{C} \). What is the electric field at 15 cm from the center?

Q4. A point charge \( 12 \, \mu\text{C} \) is at the origin. What is the electric field magnitude at a point 8 m along the x-axis?

Q5. A conducting sphere of radius 17 cm has a surface charge density of \( 15 \, \mu\text{C/m}^2 \). What is the total charge?

Q6. An infinite line charge has \( \lambda = 3 \times 10^{-6} \, \text{C/m} \). What is the electric field at 15 cm?

Q7. What property of electric charges allows them to be treated as scalars despite their ability to attract or repel?

Q8. Two charges \( +2 \, \mu\text{C} \) and \( +3 \, \mu\text{C} \) are 10 cm apart. What is the electric field at a point 5 cm from \( +2 \, \mu\text{C} \) along the line joining them?

Q9. A point charge \( -6 \, \mu\text{C} \) is at the origin. What is the electric field magnitude at a point 3 m along the y-axis?

Q10. A uniform electric field \( E = 8 \times 10^3 \, \text{N/C} \) is along the y-axis. What is the flux through a rectangle of 20 cm × 60 cm in the xz-plane?