NEET Electric Charges and Fields — Set 13

Question 1

What explains why the electric field outside a neutral object can be non-zero when placed in an external field?

Accepted Answer

Induced charge separation occurs in a neutral object under an external field, creating dipoles or surface charges. These induced charges produce their own field, which adds to the external field, resulting in a non-zero total field outside.

Question 2

A thin spherical shell of radius 25 cm has a charge of $ 15 \, \mu\text{C} $. What is the electric field at a point 30 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 = 15 \times 10^{-6} \, \text{C} $, $ r = 0.3 \, \text{m} $. $ E = 9 \times 10^9 \times \frac{15 \times 10^{-6}}{(0.3)^2} = 9 \times 10^9 \times \frac{15 \times 10^{-6}}{0.09} = 1.5 \times 10^6 \, \text{N/C} $.

Question 3

A uniform electric field $ E = 5 \times 10^3 \, \text{N/C} $ is along the y-axis. What is the flux through a square of side 40 cm in the xz-plane?

Accepted Answer

Area vector $ \Delta \mathbf{S} = (0.4)^2 = 0.16 \, \text{m}^2 $ along y-axis. Flux: $ \phi = \mathbf{E} \cdot \Delta \mathbf{S} = 5 \times 10^3 \times 0.16 = 800 \, \text{Nm}^2/\text{C} $.

NEET Physics: Electric Charges and Fields — Practice Set 13

Q1. What explains why the electric field outside a neutral object can be non-zero when placed in an external field?

Q2. A thin spherical shell of radius 25 cm has a charge of \( 15 \, \mu\text{C} \). What is the electric field at a point 30 cm from the center?

Q3. A uniform electric field \( E = 5 \times 10^3 \, \text{N/C} \) is along the y-axis. What is the flux through a square of side 40 cm in the xz-plane?

Q4. A conducting sphere of radius 19 cm has an electric field of \( 3 \times 10^3 \, \text{N/C} \) at 38 cm from its center. What is the charge?

Q5. A thin spherical shell of radius 14 cm has a charge of \( 7 \, \mu\text{C} \). What is the electric field at a point 16 cm from the center?

Q6. What fundamental principle allows the electric field due to multiple charges to be calculated as the vector sum of the fields due to each charge individually?

Q7. Why does the electric field due to a uniformly charged infinite plane sheet remain constant with distance from the sheet?

Q8. Two point charges \( 9 \times 10^{-7} \, \text{C} \) and \( -3 \times 10^{-7} \, \text{C} \) are 100 cm apart in vacuum. What is the magnitude of the force between them?

Q9. A thin spherical shell of radius 17 cm has \( q = 13 \, \mu\text{C} \). What is the electric field at 20 cm from the center?

Q10. A dipole with \( p = 4 \times 10^{-9} \, \text{C m} \) is at 30° to a field \( E = 6 \times 10^4 \, \text{N/C} \). What is the torque?