The fundamentals of magnetism and electromagnetism

Question 1

Magnets have domains, name and define the two types of domain.

Answer 1

temporary - the domains are temporarily aligned and are under the influence of magnetic fields

Permanently - the domains are permanently aligned.

Question 2

Define permeability

Answer 2

How well the material resists penetration of magnetic lines of force.

Question 3

Describe the permeability of:

1. ferromagnetic
2. paramagnetic
3. diamagnetic

Can you give any examples of these materials?

Answer 3

1. ferromagnetic - high (retains magnetism i.e. iron, steel, nickel)
2. paramagnetic - low (aluminium, copper)
3. diamagnetic - very poor with no internal magnetism. (silver, gold, water)

Question 4

What are magnetic fields and what they are represented by

Answer 4

The area in which a magnetic effect is experienced, if a magnetic material (cobalt) is placed within a magnetic field it will experience FORCE. Magnetic fields are represented by lines of force. The more concentrated these lines illustrates the magnitude of force.

Question 5

What is magnetic flux density (magnitude) measured in

Answer 5

Gauss (G) or Tesla (T)

Question 6

Magnetism …. current

Answer 6

increases

Question 7

Define what a conductor is

Answer 7

a material or substance which allows for the flow of current, they have free electrons and are low resistance.

Question 8

Define electromagnetic induction, what are the two principles that use this?

Answer 8

phenomenon where changing the magnetic field includes electromotive forces or voltage within a conductor. The principles are the motor effect and generator effect

Question 9

Define the motor effect

Answer 9

passing a current through a coil of wire within a magnetic field produces movement in the wire

Question 10

Define the generator effect

Answer 10

when introducing a rotating conductor (coil wire) into a magnetic field, the free electrons within the conductor will flow to the positive end therefore generating electricity.

Question 11

Describe Faradays laws of electromagnetic induction

Answer 11

1.When magnetic lines of force are cut by a conductor an Electro Motive Force (EMF) is induced in that conductor.

2. The induced EMF is proportional to the number of lines cut (field strength) and the rate at which they are cut.

So – induction depends upon magnet strength and oscillations.

Question 12

When is electromotive force (EMF) used?

Answer 12

when the source of electricity is a battery generator or transformer coil

Question 13

define transformer

Answer 13

an electrical device which is used to change alternating voltages from one level to another

Question 14

Name the two types of transformer that are used in x-ray tube and x-ray tube cabinets

Answer 14

step up transformer - x-ray tube
high tension transformer - x-ray tube cabinets