Electrostatic Flashcards
What is electrostatic?
It is a system where source charges are at rest, no magnetic field, conservative and Irrotational field.
What is a field?
A field is a spatial distribution of quantises such as scalar values and vectors, which may or may not be varying in time. It is a description of what to find for each point in the field.
What is the electric field intensity?
The electric field intensity is the force pr unit charge that a test charge at rest experiences when placed in an electric field.
What are the two fundamental postulates of electrostatics?
The divergence of the electric field intensity is the charge density divide with the permittivity in free space.
∇∙E=ρ/ϵ0
The curl of the electric field intensity is zero, this means that the electric field intensity is an irrational (conservative) vector field.
∇×E=0
What is the Integral forms?
Gauss Law tells us her that total flux of the electric field intensity is equal to the total enclosed charge divide with the permittivity in free space.
Stokes Law tells us her that total scalar line integral of the electric field intensity around a closed path vanishes.
What is the connection to Kirchoff´s Voltage law?
Because the dot product of the electric field and the change in length is the voltage, since the electric field vanishes around a closed path the voltage also vanishes.
What is Coulomb´s Law?
The force between to point charges are the proportional to inverse square of the radius between them.
What is electric dipole and dipole moment p?
Electric dipole is where there is a pair of equal charges with opposite charge, speared by a small distance d.
An electric dipole moment p is a product of the charge q and the distance d. Which is a vector.
What does Gauss law tell us?
That the outward flux of the electric field intensity over any surface in free space is given as the total enclosed charge density divide with the permittivity.
Gauss Law is especially useful in situation where symmetry can be applied since the normal component is constant over the enclosed surface.
What is the electric potential?
It is a field that only works in the electrostatics, since the electric field is irrotational because the curl of the electric field is zero, we can use gradient of some scalar field and find the electric field.
E=-∇V
Why the minus sign?
Because the potential energy (electric potential) goes against the field.
The field tells us how much work is need for a charge to move against the electric field.
What is electrostatic voltage?
It is the difference in electric potential for two points.
Why is it easier to find V than E?
If Gauss Law does not work, It way easier to find the electric potential and then find E.
And scalar quantities are just easier to handle than vector quantities.
