Quizzes Flashcards
Where are the forces of a magnet the strongest?
At the poles
What was the first compass made out of?
magnetite, wood, water
The North pole of a compass is the _____ ______ pole of the earth
magnetic south
Three basic types of magnets?
Natural
Artificial
Electromagnets
What magnets are man-made?
Artificial, Electromagnets
Magnetic materials that are easily magnetized?
ferromagnetic
Metals that are not as easily magnetized?
Paramagnetic
Metals or non-metals that cannot be magnetized?
diamagnetic
Four characteristics of flux lines?
- always complete a loop
- never cross
- have no insulator
- more dense closer to the conductor
When will there be a magnetic field around a conductor?
When there’s current flow
Formula for finding force between parallel conductors?
Fm= k x I1x I2 /d2
A spiral shaped coil is called?
a helix
A helically wound coil that produces a strong magnetic field is called?
A solenoid
What 4 factors affect the strength of an electromagnet?
- number of turns
- core material
- spacing between
- vary current through the coil
What is the device called that must be used to store a horseshoe magnet?
Keeper
Which direction do magnetic lines of force flow (outside the magnet)
North to South
The property that opposes the setting up of flux lines is called?
Reluctance
What type of material would you use to make a magnetic screen?
soft iron
When would magnetic lines of force repel each other?
When facing opposite
When would magnetic lines of force attract each other?
When facing each other
Name three ways to produce artificial magnets?
- DC current
- tapping or vibrating
- stroking with a magnet
What is permeability?
The ease of setting up flux lines
What do we use to determine the permeability?
BH graph
What is it called when all of the domains are aligned with the magnetic field?
saturation
What is the difference between “theoretical saturation” and “practical saturation”?
Theoretical - all domains perfectly arranged
Practical - When domains are almost aligned and it is not practical to align them perfectly
What is the point called in which the flux density has hit practical saturation?
Knee
The magnetizing curve that is plotted on the graph is called?
hysteresis loop
What is residual magnetism?
the amount of flux density that remains in the material
What is coercive force?
Amount of force to remove the residual magnetism
Which one would have greater flux? (Iron core or Air core)
Iron core
AC magnetic cores are usually made from high ___________________ and low _____________?
electrical resistance
retentivity
What determines polarity of an electromagnet?
power source
By increasing the current the ___________________ would increase as well?
MMF
