Lecture 1: Magnetic Fundamentals

Question 1

What produces a magnetic field?

Answer 1

A moving charge (current)

Question 2

Who first illustrated that a moving charge (current), produced a magnetic field? and when?

Answer 2

Orested in 1819

Question 3

Who is Ampere? and What did he do?

Answer 3

Ampere in 1820, quantified this relationship showing that magnetic field is proportional to moving charge (current)

Question 4

Who is Faraday? Why is he important?

Answer 4

Faraday in 1831 noted the inverse was also true. That magnetic field can produce moving charge (current)

Question 5

Give three characteristics of magnetic fields

Answer 5

1. always complete loops (no start or end like electric field lines)
2. always go from north to south
3. never intersect each other

Question 6

B is?

Answer 6

flux density

Question 7

B is measured in?

Answer 7

Tesla’s (T) or Wb/m2

Question 8

H?

Answer 8

Field intensity

Question 9

H is measured in?

Answer 9

At/m

Question 10

Define permeability

Answer 10

is a a measure of how easily something is magnetised

Question 11

What is a solenoid?

Answer 11

A solenoid is a conductor coiled around a small area numerous times.
Coil - large area - few turns

Question 12

Faradays law?

Answer 12

IF the imaginary surface is bounded by a conductor, then as the flux changes in the area, a voltage is induced

Question 13

Lenz Law?

Answer 13

the current induced in a closed loop, due to changing magnetic flux, is such that opposes the change in flux

if flux decreases - current flows in constructive direction to magnetic field

if flux increases - current flows in destructive direction to magnetic field

Question 14

Flux Linkage?

Answer 14

For more than one loop, the induced voltage is summative

Question 15

List and explain three types of magnets

Answer 15

1. ferromagnetic
2. paramagnetic
3. diamagnetic

F: remains after magnet taken away
D: Creates at least a pair of electrons after magnetized
P: after magnetic field removed, it has no aligned dipoles

Question 16

What are B-H curves used for?

Answer 16

illustrate permeability and magnetization curves of the magnets.

P+D are linear and constant perm. however F saturates and no more aligned dipoles regardless of current