Three Kind of electrostatics problem(quite )

[sunumen]

Three Kind of electrostatics problem(quite urgent)

Homework Statement

The first kind of prbolem is about the dielectric coefficient
http://myweb.polyu.edu.hk/~07190086d/phy/q1.zip

I know the equations below
but I don't know how to relate the E-field into eqn1
The main reason is that I don't know is the D related in this kind of problem?

Homework Equations

Q1:
(eqn1)
$$\frac{tan\alpha1}{tan\alpha2}$$ = $$\frac{K1}{K2}$$
where alpha1 is incidence angle
K is dielectric coefficient

D=$$\epsilon$$E
where D is electric displacement
E is E-field

K=$$\epsilon$$/$$\epsilon$$o

where $$\epsilon$$o is the permittivity of dielectric
$$\epsilon$$ is the permittivity of vaccum


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Homework Statement

The second type of problem is about the simplest electrostatic problem!
http://myweb.polyu.edu.hk/~07190086d/phy/q2.zip
I don't really understand the meaning of "potential" is zero.
Doesn't the potential is set by us?
I know that when the net force is zero, then the PE should be minimum.
But these problems make me very confusing.


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Homework Statement

The last kind of question is about the leakage and capacitance.
http://myweb.polyu.edu.hk/~07190086d/phy/q3.zip

The equation related:
RC=$$\epsilon$$/$$\sigma$$
where $$\sigma$$ is lossy dielectric of conductivity

I cannot really remember the previous concept of capacitance very well
but I know that the time constant(decay to half ) is RC

this problem are something new for me
and I want to know how to use the idea of lossy dielectric of conductivity

 

[lippyka]

to solve this kind of problem.The Attempt at a Solution For the first type of problem, you can use the equation D=εE to relate the E-field to the equation. This means that the electric displacement is equal to the product of the permittivity of the material and the electric field. For the second type of problem, when you set the potential to be zero, it means that you are setting the potential energy of the system to be zero. This means that the net force on each particle must be zero, since the potential energy is the sum of the forces acting on the particles. For the third type of problem, you can use the equation RC=ε/σ to calculate the capacitance of the system. This equation states that the time constant (the time it takes for the voltage to decay to half its original value) is equal to the product of the resistance and capacitance of the system. The lossy dielectric of conductivity (σ) is used to account for any losses in the system due to the dielectric material used.

 

[Moetasim]

in this kind of problem

I understand your concerns and confusion regarding these three types of electrostatics problems. Let me provide some clarification and guidance to help you better understand and approach these problems.

Firstly, for the first type of problem involving the dielectric coefficient, it is important to understand that the dielectric coefficient is a measure of how well a material can store electrical energy. In this type of problem, we are typically given two materials with different dielectric coefficients and are asked to find the relationship between the incident angle and the dielectric coefficients. To relate the E-field to eqn1, you can use the electric displacement D=\epsilonE, where D is related to the electric field E by the permittivity of the material. This will help you solve for the relationship between the incident angle and the dielectric coefficients.

Moving on to the second type of problem, it is important to understand the concept of potential. In electrostatics, potential refers to the amount of work required to move a unit charge from one point to another against an electric field. In this type of problem, when the potential is set to zero, it means that there is no potential difference between the two points, and hence no work is required to move a charge between them. This is often used as a reference point in electrostatics problems. Remember that potential is a scalar quantity, and it is the difference in potential between two points that is important in determining the electric field and forces.

Lastly, for the third type of problem involving leakage and capacitance, it is important to understand the concept of capacitance. Capacitance is the ability of a material to store electrical energy. In this type of problem, we are typically given a lossy dielectric material with a certain conductivity and are asked to find the time constant, which is given by RC=\epsilon/\sigma. Here, the time constant is the time it takes for the charge to decay to half its original value. To use the idea of lossy dielectric of conductivity, you can use the equation RC=\epsilon/\sigma and solve for the time constant.

I hope this response has helped clarify some of your concerns and provided some guidance on how to approach these types of electrostatics problems. Remember to always understand the concepts and equations involved before attempting to solve the problems. Good luck!