A spherical charged conductor has surface densityσof charge. The...
E = KQ/R2
= Kσ(4πR2)/R2
= σ/ε0
R ----> 2R and σ = unchanged
E' = Kσ[4π(2R)2]/(2R)2
=> σ/ε0 = E
A spherical charged conductor has surface densityσof charge. The...
Understanding Electric Field on a Charged Sphere
When dealing with a spherical charged conductor, the relationship between surface charge density, electric field, and radius is crucial for understanding how changes affect the overall electric field.
Surface Charge Density
- The surface charge density (σ) is defined as the charge per unit area on the surface of the sphere.
- It remains constant when the radius of the sphere is doubled.
Electric Field on the Surface
- The electric field (E) just outside the surface of a charged conductor can be expressed using the formula:
E = σ / ε₀, where ε₀ is the permittivity of free space.
- This formula shows that the electric field on the surface is directly proportional to the surface charge density.
Doubling the Radius
- When the radius of the sphere is doubled (2R), the surface area increases since the surface area of a sphere is given by 4πR².
- The new surface area becomes 4π(2R)² = 16πR², which is four times the original surface area.
Charge Conservation
- If the total charge remains the same, the surface charge density on the new sphere (with radius 2R) will decrease because the same charge is spread over a larger area.
- New surface charge density σ' = Q / (4π(2R)²) = Q / (16πR²) = σ / 4.
Conclusion on Electric Field
- Applying the formula for electric field with the new surface charge density:
E' = σ' / ε₀ = (σ / 4) / ε₀ = E / 4.
- Therefore, the electric field on the surface of the new sphere is E/4, confirming that the correct answer is option 'B'.