Electricity

Question 1

What is the Gauss’ Law in integral form?

Answer 1

∯S E × dS = ∭v (ρ / ε0) dV

Where:
∯S = Surface integral
E = Electric field at the surface
S = Surface Area

∭v = Volume integral
ρ = Volume charge density
ε0 = Permittivity of free space
V = Volume

Question 2

What are electrical conductors?

Answer 2

Electrical conductors are materials in which some of the electrons are free electrons that are not bound

and can move relatively freely through the material.

Question 3

What are electrical insulators?

Answer 3

Electrical insulators are materials in which all electrons are bound to atoms

and cannot move freely though the material.

Question 4

What type of material’s properties are somewhere between those of insulators and conductors?

Answer 4

Semiconductors.

Question 5

What is Coulomb’s Law?

Answer 5

F = k (q1 × q2) / r^2

Where:
F = Electric force
k = Coulomb constant
q1, q2 = Charges
r = Distance of separation

Question 6

What is Coulomb’s constant equal to?

Answer 6

k = 1 / 4πε0

Question 7

What is Gauss’ Law in differential form?

Answer 7

∇ E = ρ / ε0

Question 8

Describe what is meant by the electrostatic energy of a system.

Answer 8

The energy is defined as the work we do

to overcome the electric forces of the existing charges

when we assemble the charge system (from infinity)

to their eventual positions.

Question 9

In a linear dielectric material, the electric displacement field and the electric field have a linear relationship:

Answer 9

D = P +ε0E = εε0E

Where:
D = electric displacement field
P = polarization field
E = electric field
ε = relative permittivity of dielectric material
εε0 = permittivity of material

Question 10

What is the equation for the electric field as a gradient of potential?

Answer 10

E = - ∇φ

Where:
E = electric field
φ = electric potential