Magnetism & Electromagnets Flashcards
Magnetic moments align to form …
Domains
What type of magnet do speakers use?
A permanent magnet
A point on a magnet where the force of attraction is strongest?
A Pole
The magnetic effect of a material is caused by this atomic particle?
An electron
Lines of magnetic force around a magnet are called…
Flux
Lines of flux flow from which pole?
The North Pole
What is magnetite?
A naturally occurring magnetic material.
Magnetic flux is symbolized by what Greek letter?
Phi
Which pole do magnetic lines of flux flow into?
The South Pole
What is reluctance?
The opposition to magnetic flux
What is saturation?
When the maximum magnetism of a material is reached.
List three factors that affect the strength of an electromagnet.
- The amount of current in the coil.
- The number of turns on the coil.
- The type of core that is part of the magnetic field.
Define hysteresis losses
It is the undesired heat production from the flip-flopping of the magnetic domains.
The heat produced by circulating currents in the core caused by the changing magnetic field are called?
Eddy currents.
What are two methods that are used to reduce the effects of hysteresis losses and eddy currents?
Silicon steel and laminations between sheets in the core.
What is the symbol for Inductance and what is its unit of measurement?
“L” and the unit of measurement is henry (H)
Creating a voltage on a different circuit from the source when they share the same core is called?
Mutual inductance
Using the left hand rule for COILS, the fingertips point in the direction of _________ and the thumb indicates __________.
- Electron Flow
2. North Pole
What is Lenz’s Law defined as…
Induced voltage opposes the cause that produced it.
What is a magnet that’s created by energizing a coil of wire?
An electromagnet
Define retentivity
It is the ability of a material to retain magnetism
What is permeability
It is a material property that determines the ease with which magnetic flux magnetizes that material.
Materials used to make permanent magnets are?
Cobalt
Molybdenum
Chrome-tungsten and
Alnico - which is the most common
What are permanent magnets used for?
Permanent magnet motors Magnetos Megohmmeters Speakers and Analog meters
