# How an Electric Field is affected by an Insulator

• Iftekhar Uddin
In summary, the electric field at the surface of the cardboard cylinder is zero, and the electric flux through the cylinder is also zero.
Iftekhar Uddin
I looked through this forum post for an answer to my problem. It gave me enough insight to try and come to some conclusions but I'm still confused on some parts here and there about how I got my final answer.

1. Homework Statement

A uniformly charged, straight filament 7.70 m in length has a total positive charge of 2.00 µC. An uncharged cardboard cylinder 1.50 cm in length and 10.0 cm in radius surrounds the filament at its center, with the filament as the axis of the cylinder.
(a) Using reasonable approximations, find the electric field at the surface of the cylinder.

(b) Using reasonable approximations, find the total electric flux through the cylinder.

## Homework Equations

The Electric Field of a filament is λ/2πRε
λ=Total charge/length

## The Attempt at a Solution

(I got the solution but I have questions about part A)
[/B]
* I found that the answer to A was the electric field of a filament with r = .1m. I used this equation on an earlier problem that asked for the electric field at x distance away from the filament. But this is the same for this cardboard cylinder? I don't have to multiply it by the length of the cylinder? Why? The only reason I could think for this is that I'm finding a uniform E so I'm just finding E at a distance of R radially. Is that correct?

* Is cardboard not an insulator? If so, it doesn't affect the electric field at all? I thought that as an insulator it'd affect the electric field so that the outside surface of the insulator would have an E of 0.

As far as I remember, The net electric field is less than the applied electric field because it will create dipoles and will have an electric field opposite to the applied so it becomes less. However it can never be zero inside or outside.

It should give you the dialectic constant of the cardboard.
Someone can confirm this.

Hmmm maybe I'm not far enough into physics for this because I got the right answer without adjusting for this dipole situation.

## 1. How does an insulator affect an electric field?

An insulator affects an electric field by resisting the flow of electric charges. This causes the electric field to become weaker within the insulator, as the charges are unable to pass through it.

## 2. Why do insulators have a lower electric field than conductors?

Insulators have a lower electric field than conductors because they have a higher resistance to the flow of electric charges. This means that the charges are unable to move freely and the electric field becomes weaker within the insulator.

## 3. Can an insulator completely block an electric field?

Yes, an insulator can completely block an electric field. This is because the resistance of the insulator prevents the electric charges from passing through, creating a barrier that stops the electric field from reaching the other side.

## 4. How do insulators affect the movement of electric charges within an electric field?

Insulators limit the movement of electric charges within an electric field. This is because the charges are unable to flow freely through the insulator, causing the electric field to become weaker within the insulator.

## 5. What factors determine the strength of the electric field within an insulator?

The strength of the electric field within an insulator is determined by the resistance of the insulator and the amount of charge present. Higher resistance and lower charge will result in a weaker electric field within the insulator.

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