Midterm 1

Question 1

Faraday’s Law

Answer 1

Induced emf in any closed circuit is equal to the rate of change of the magnetic flux over time. This induced emf creates a current, which opposes the flux causing it (Lenz’s effect)

Question 2

Ampere’s Law

Answer 2

Ampère’s circuit law states that the line integral of H around a closed path is the
same as the net current Ienc enclosed by the path

Question 3

Stoke’s Law

Answer 3

Stokes’s theorem states that the circulation of a vector field A around a (closed) path
L is equal to the surface integral of the curl of A over the open surface S bounded
by L
(see Figure 3.21), provided A and   A are continuous on S.

Question 4

Gauss’s Law (general)

Question 5

Gauss’s Law (magnetism)

Answer 5

An isolated magnetic charge does not exist

Question 6

Lenz’s Law

Answer 6

Induced emf creates a current whose related magnetic flux will oppose the change in direction of the magnetic flux inducing the emf (conservation of energy)

Question 7

Get from H to B

Answer 7

B=uH

Question 8

What is H?

Answer 8

Magnetic field strength
Units: A/m (Amperes per metre)

Question 9

What is B?

Answer 9

Magnetic flux density (B for Bensity)
Units: Tesla

Question 10

What is D?

Answer 10

Electric flux density
D=ϵE
Units: C/m^2

Question 11

What is ϵ?

Answer 11

Permittivity
Units: H/m (Henries per metre)

Question 12

What is µ?

Answer 12

Permeability
Unit: F/m (henries per metre)

Question 13

What is eta? (curly n)

Answer 13

Impedance of the medium
Units: Ohms

Question 14

What is n?

Answer 14

Refractive index
n = sqrt(µrϵr)

Question 15

What is beta?

Answer 15

Wave number or the propagation constant
beta=2*pi/λ

Question 16

λ

Answer 16

Wavelength
Inverse of fs, spatial frequency

Question 17

-sin(wt)=

Answer 17

cos(wt+pi/2)

Question 18

Steps to derive the wave equation (in terms of Ex)

Answer 18

• Start with curl of E = -dB/dt
• B=uH
• cross of E =duHy/dt
• y component of cross of E = -udH/dt
• dEx/dz=-udHy/dt
• Then switch to cross of H = J + dD/dt
• J = 0
  same process as before to get
  x component of cross of H = edE/dt