Chapter 8/9 Electromagnetism Flashcards
What are magnetic fields used for?
Operate Electrical Controls
Operate Motors
Lift Equipment
Operate Transformers
Like magnetic poles ? and unlike magnetic poles ?
Repel
Attract
What is the Theory of Magnetism?
The ability of a material to be magnetic is because of the spin of the electrons in the material.
That each domain acts likes a small permanent magnet
Electrons have an ? around them.
electrostatic field
The lines of force from an electron’s electrostatic field travel ?
Towards the center of the electron
An electron is like a small electromagnetic because,
The electron spins on its axis, causing its electrostatic field and magnetic fields to cross.
Do all electrons spin in the same direction?
No
Electrons that are in the same shell and spin in opposite directions cause?
The magnetic properties of the electrons to cancel out.
How do some material exhibit the characteristics of a magnet?
Unpaired electrons are spinning in the same direction. This causes aiding magnetic fields.
Electrons change their spin characteristics based on ?
Temperatures
Very High- Demagnetize
Very Cold- Prevalent
What is Domain Theory?
Magnetic blocks exists in magnetic materials, when these magnetic blocks are aligned in the same direction, using magneto-motive force, the stronger the magnetic material becomes.
What are the laws of magnetism?
- Energy is required to create a magnet (magnetic field), but no energy is required to maintain a magnet (magnetic field)
- Like Poles repel, Unlike poles attract
- The magnetic force between two poles is directly proportional to the pole strength, and inversely proportional to the square of the distance between them.
The effect of a magnet to be able to retain magnetism is ?
retentivity
In dealing with magnetism, materials are classified into three categories, what are they?
Ferromagnetic, Paramagnetic, and Diamagnetic
Ferromagnetic materials can be ? why ?
easily magnetized
The magnetic domains align easier
Paramagnetic materials are
weakly attracted to magnets
Diamagnetic materials ?
repel magnetic flux, create a very weak magnetic field in the opposite direction
How does shielded cable work?
The shield is made of a Paramagnetic material and acts like a magnetic shield disrupting the flux from electromagnetic sources, that would induce a voltage into the wire.
The shield is grounded at one end of the cable to take any induced voltage and current to ground protentional.
A magnetic field is produced when ?
Current flows through a conductor
The direction in which the field encircles the conductor can be remember by using ?
The left hand rule for a conductor
The magnetic field from a conductor is a ? field. Which means?
Concentric- originates at the center of the conductor and moves out in unbroken circles perpendiculars to electron flow.
The size of the magnetic field is proportional to ?
the amount of current flow.
Natural magnets were first known by the name ?
Magnetite
A material that retains its magnetic properties is called a permanent magnet, and one that loses this characteristic easily is called a ? magnet.
temporary
The cores of temporary magnets are usually made of ?
Iron
Magnetic lines of force are called lines of ? .
Flux
The point at which the magnetic domains of a material are all lined up is called ?
saturation
