Physics - Dielectrics

This will be an introduction to dielectrics. Dielectrics are insulators that are mainly used to fill the gaps within capacitors in order to increase the capacitance it can hold. The Dielectric actually weakens the electric field within the capacitor as the electrodes induce a charge on the surfaces of the insulator, but this effect will never completely reverse the electric field.

A Dielectric has a property called electric susceptibility which is designated by Χ_e. This is a multiplier of the electrical permittivity of free space ε₀. This susceptibility is pretty much always an increase meaning its value is greater than one and can range up to 300 times larger depending on what you use as a dielectric. Therefore its effect on a capacitor can be thought of as simply changing the permittivity of free space to the permittivity of the material of the dielectric while keeping the rest of the equations that govern a capacitor the same.

There are other phenomena to be examined but in general they correspond to the insertion or removal of a dielectric, which does not have many applications as they are mainly used to enhance capacitors.

Back to ToC

Physics - Series and Parallel Effects for Basic Electronic Parts

This will be an overview for the effects of putting basic electronic components in series or parallel connections.

• Series
• Capacitors
• Add as reciprocals 1/C_tot = 1/C₁ + 1/C₂ ...
• Resistors
• Add normally R_tot = R₁ + R₂ ...
• Inductors
• Add normally L_tot = L₁ + L₂ ...
• Parallel
• Capacitors
• Add normally C_tot = C₁ + C₂...
• Resistors
• Add as reciprocals 1/R_tot = 1/R₁ + 1/R₂ ...
• Inductors
• Add as reciprocals 1/L_tot = 1/L₁ + 1/L₂ ...

However there are additional rules with Inductors as the magnetic field of an inductor can affect nearby inductors. Also when there are only two things to add as reciprocals, can change the equation to C_tot = C₁C₂ /  C₁ + C₂

Back to ToC

Physics - Parallel Plate Capacitor

This will be an introduction into the basic physics of a capacitor. A parallel plate capacitor is when we have two electrodes placed a distance d apart. One is charged Q and one is charged -Q which means that the capacitor doesn't have any net charge. Therefore with the exception of a small fringe field at the edges of the the capacitor we don't have a field when we view a capacitor from afar we don't see a net electric field.

The electric field within the electric field is due to both plates. The field form the positive plate points away form the plate in this case to the right, and the electric field from the negative plate points towards the plate which is also the right. Therefore

E = Q/ε₀A

This is an approximation for infinitely sized parallel plate capacitors but this is actually a good approximation for real world capacitors assuming d is much smaller than the size of the electrodes.

Back to ToC