Math Problem Statement
An infinite conducting cylindrical shell has radius 0.15 m and surface charge density 1.1 μC/m2. What is the magnitude of the electric field, in newtons per coulomb, 1.1 m from the axis of the cylinder? Keep in mind: Make use of cylindrical symmetry. Can you determine the total charge per unit length of the cylinder? The surface area of a cylinder (excluding the ends) is 2πrL.
Solution
Let's break the problem down step by step.
Step 1: Understanding the setup
- We have an infinite conducting cylindrical shell.
- The shell has a radius of 0.15 m.
- The surface charge density is given as .
- The electric field is to be calculated at a distance of 1.1 m from the axis of the cylinder.
Step 2: Total charge per unit length on the cylindrical shell
The total charge per unit length, , on the cylindrical shell can be determined by multiplying the surface charge density by the surface area of the cylindrical shell per unit length (assuming length = 1 meter). The surface area per unit length of a cylindrical shell is:
Now, the charge per unit length is:
So, the charge per unit length is:
Step 3: Electric field at a distance of 1.1 m from the axis
Using Gauss's Law, we can find the electric field at a distance from the axis of the cylindrical shell. Because of cylindrical symmetry, the electric field will be radial and depend only on the distance from the axis.
Gauss's law for a cylinder states that:
Where:
- is the electric flux.
- is the charge enclosed by the Gaussian surface.
- is the permittivity of free space ().
For a cylindrical Gaussian surface with radius and length , the electric flux is:
The enclosed charge is the charge per unit length times the length of the Gaussian surface:
Thus, Gauss's law becomes:
Simplifying for :
Substitute the known values:
Now let's calculate the electric field:
Final Answer:
The magnitude of the electric field at a distance of 1.1 m from the axis of the conducting cylindrical shell is approximately:
Do you want any additional details or have other questions about this? Here are some related topics to explore:
- How does the electric field change if the distance from the cylinder is less than the radius of the shell?
- How do the electric fields inside and outside a conducting cylindrical shell compare?
- What would happen to the electric field if the shell was not conducting?
- What would happen if the shell had a different surface charge density?
- Can you apply Gauss’s Law to other symmetrical charge distributions like spherical or planar symmetry?
Tip: When using Gauss’s Law for cylindrical symmetry, always choose a Gaussian surface that matches the symmetry of the problem, such as a co-axial cylinder.
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Math Problem Analysis
Mathematical Concepts
Electrostatics
Gauss's Law
Cylindrical Symmetry
Formulas
Surface Area of Cylinder: A = 2πrL
Charge per Unit Length: λ = σ * A
Electric Field using Gauss's Law: E = λ / (2π * ε₀ * r)
Theorems
Gauss's Law
Suitable Grade Level
College/University Physics
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