Answer:
Step-by-step explanation:
Here is the definition of each variable used in the expression for the electric field strength:
• r: radial distance from the center of the shell to the point where the electric field strength is being calculated
• a: radius of the shell
• b: thickness of the shell
• ρ_0: charge density in the shell
• ε_0: permittivity of free space, a constant that relates the electric flux density to the electric field strength. Its value is approximately 8.854 x 10^(-12) C^2/Nm^2.
• E: electric field strength, a vector quantity that describes the force experienced by a unit positive test charge placed at a particular point in an electric field.
• ∇: the gradient operator, a vector differential operator that describes the rate of change of a scalar field with respect to position.
• ∫: the definite integral symbol, denoting the sum of an infinite number of infinitesimal quantities over a specified range.
• dr': infinitesimal element of the radial distance used in the integration over the shell.
The electric field strength in a region is given by the gradient of the electric potential, V, in that region. The electric potential is related to the charge distribution, ρ, by the Poisson equation:
∇^2V = -(1/ε_0) * ρ
where ε_0 is the permittivity of free space.
If we assume the charge distribution is spherically symmetric, such that ρ = ρ(r), we can express the electric potential as:
V(r) = (1/4πε_0) * ∫(ρ(r')/|r-r'|) dV'
We can simplify this expression by assuming that the charge distribution is confined to a thin shell of radius a and thickness 2b, so that ρ(r) = ρ_0 for a-b <= r <= a+b and ρ(r) = 0 elsewhere. The electric potential in the region a can then be calculated by integrating over the shell:
V(r) = (1/4πε_0) * ρ_0 * ∫_{a-b}^{a+b} (1/|r-r'|) * dr'
To find the electric field strength, we need to take the gradient of the electric potential:
E = -∇V
Substituting in the expression for the electric potential, we get:
E = -∇[(1/4πε_0) * ρ_0 * ∫_{a-b}^{a+b} (1/|r-r'|) * dr']
So, the electric field strength in the region a is proportional to the gradient of the integral of the charge distribution over the shell, and is expressed in terms of the radius, a, the thickness, b, the charge density, ρ_0, and the permittivity of free space, ε_0.