Calculate E - capacitor question

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In summary, the conversation discusses a parallel plate capacitor with square plates of side L and distance d<<L apart. A block of dielectric material can fill the space between the plates, with the dielectric composed of two materials with different dielectric constants. The dielectric can move without friction along the x axis and outside the capacitor. The conversation then considers the definition of electric field and electric displacement field and how to calculate their values in the region between the plates for three different possible regions: when the space is occupied by material 1, material 2, and vacuum.
  • #1
blueyellow

Homework Statement



Consider a parallel plate capacitor with square plates of side L and distance d<<L apart. The bottom plate lies on the x-y plane, and the distance d is parallel to z. A block of dieletric material can completely fill the space between the plates.

Consider the dieletric to be composed of two materials glued together, material 1 with dieletric constant epsilon1 and dimensions 0.6L*L*d (in x, y and z directions, respectively) and material 2 with constant epsilon2 and dimensions 0.4L*L*d. The dielectric is free to move as a single block without friction along the x axis, parallel to the plates inside the capacitor, and it can also move outside the capacitor. Let us define as x the distance between the dielectric and the edge of the plates, and we can neglect the electric field outside the plates. Considering that the potential difference between two points a and b is delta V= integral from a to b of E.dl, and that D=epsilon0*epsilon(subscript r)*E, where epsilon(subscript r) is the dielectric constant, calculate the value of the electric field E and of the electric displacement field D in the region between the plates, for the three possible regions where the space is occupied by the material 1, the one with material 2, and the vacuum.

Homework Equations

 
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  • #2
attempt at solution:

E=q/(epsilon0 *A)



E=deltaV/d

= integral from a to b of E.dl /d



E=-grad V



but all this seems to be leading nowhere.
 

1. How do I calculate the value of capacitance for a given E-field?

The formula for calculating capacitance is C = E/A, where C is capacitance, E is electric field strength, and A is the area of the plates. So to calculate the value of capacitance, you need to know the electric field strength and the area of the plates.

2. How do I convert between different units of E-field and capacitance?

To convert between different units of E-field and capacitance, you can use the following conversions: 1 V/m = 1 N/C, 1 F = 1 C/V, and 1 pF = 1e-12 F. For example, if you have an electric field strength of 10 V/m and want to convert it to N/C, you would multiply 10 by 1 to get 10 N/C.

3. What is the relationship between E-field, capacitance, and voltage?

The relationship between E-field, capacitance, and voltage is given by the formula V = Ed, where V is voltage, E is electric field strength, and d is the distance between the plates. This formula shows that the voltage across a capacitor is directly proportional to the electric field strength and the distance between the plates.

4. How do I calculate the energy stored in a capacitor?

The energy stored in a capacitor can be calculated using the formula U = (1/2)CV^2, where U is the energy, C is capacitance, and V is voltage. This formula shows that the energy stored in a capacitor is directly proportional to the capacitance and the square of the voltage.

5. How does the dielectric material affect the E-field and capacitance of a capacitor?

The dielectric material between the plates of a capacitor can affect the E-field and capacitance in different ways. The dielectric material can increase the capacitance of a capacitor by reducing the electric field strength between the plates. It can also decrease the capacitance if it has a lower dielectric constant than air. Additionally, the dielectric material can store energy in the form of electric polarization, which can increase the energy stored in the capacitor.

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