First Half Flashcards
1
Q
Electrostatic field
A
means curl = 0 as no time derivative so must be static
2
Q
Potential
A
=Integral of E.dl
3
Q
To find potential
A
- Use E.dl from arbitrary point
- Easiest path is 3 pieces (X to Xo, then Y to Yo, Z to Zo) [as eliminate 2 other dot products for each path]
- Careful for where variables cancel vs where they are Xo, Yo or Zo
4
Q
How to find electric field from potential
A
Partial derivatives (divergence)
5
Q
Poissons equation
A
- the Laplacian of the electric potential field is equal to the volume charge density divided by the permittivity, with a change of sign.
- Derived from divergence of electrostatic field (nabla . E = Rho/epsilon o) and a E = -nabla V
6
Q
Laplace
A
Second partial derivative
7
Q
3 equations for static fields
A
- Curl = 0
- Field = - gradient of potential
- Divergence of mu H or epsilon E = 0
8
Q
Ferromagnetism
A
T
9
Q
H field
A
= B/muo - M vector
10
Q
J free
A
= curl of H
11
Q
When solving problems with magnetism and bound currents
A
Either use magnetisation with no bound currents, or use bound currents only
12
Q
J bound
A
= curl of magnetisation
