7) Magnetism and Electromagnetism Flashcards
How many poles do all magnets have?
- 2
- North and South
What is a magnetic field?
a region where magnetic materials experience a force
What direction do magnetic field lines always go?
from North to South
A _________ magnet produces its own magnetic field
permanent
What is an induced magnet?
a material that becomes a magnet when it is placed in a magnetic field
What is a magnetically soft material?
a material that loses its induced magnetism (iron)
What is a magnetically hard material?
a material that will retain some of its induced magnetism (steel)
How could you investigate the magnetic field of a magnet?
- use iron filings and scatter them on a page, place a magnet under the page, tap the paper until the iron filings are in a clear pattern
- use plotting compasses, move them around a magnet and mark the north and south poles, keep repeating this and then join all the points together to create the field lines
When is Fleming’s left hand rule used?
to find the the direction of the force on a current in a magnetic field (motor effect)
What is the motor effect?
when a current flows through a wire in a magnetic field a force is produced
What happens if you increase the current in the motor effect?
the force will be bigger
How do DC motors work?
- a split ring commutator changes the direction of the current every half turn to allow the motor to keep spinning in the same direction
What would happen to the motor without the commutator?
the motor would spin and then stop at 180 degrees
How would your increase the speed of a motor?
- increase the current
- increase number of turns in coil
How would you make the motor spin in the opposite direction?
- reverse the direction of the current
- reverse the direction of magnetic field lines
