Electromagnetism Flashcards
When is a magnetic material considered soft and hard
-it is considered soft if it loses its induced magnetism quickly, or hard if it keeps it permanently
Example of a hard and soft magnetic material
Iron is a soft magnetic material and steel is a hard magnetic material
How to increase the strength of a magnetic field
-increase the number of turns(not coils)
-wrap solenoid around a soft iron core
-increase the current
Motor effect
-when a current-carrying wire is placed in a magnetic field,
such that the wire cuts the field lines (strongest when perpendicular), the magnetic field
of the permanent magnet and the wire interact, so there
is a force acting on the wire. (This is called the motor
effect)
Explain how a d.c. motor works
-motor is powered by a battery which supplies direct current
-current flows from + to - passing through the brush and commutator, then around the coil
-this couple of forces provides a turning moment to turn the coil
-as the coil rotates, the brushes stay in their fixed position, while the split-ring commutator, being attached to the coil, rotates
How does a loudspeaker work using the motor effect
-a.a electrical signals from an amplifier are fed to a coil of wire in the speaker which is wrapped around the base of a cone
-the coil is surrounded by a permanent magnet, so the a.c. Signals cause a force on the coil and make it move back and forth
-these movements make the cone vibrate and creates sounds
what is a magnetic field
a region where magnetic materials experience a force
which way do magnetic field lines point
north to south
practical to find magnetic field lines
-use multiple compasses to see the magnetic field lines coming out of a bar magnet or between two bar magnets
-or put magnet under a piece of paper and scatter the iron fillings on top and tap the paper until the iron fillings form a clear pattern
how is magnetism induced into magnetic materials
-when magnetic materials are brought near to a magnet, that material acts as a magnet
-the stronger the magnet and the magnetic material get, the stronger the induced magnetism will be
how can you use magnetic field lines to create a uniform magnetic field
place a north pole next to a south pole of two permanent magnets near each other
properties of uniform magnetic fields
always the same strength and the field lines are the same distance apart and pointing in the same direction
magnetic materials
-nickel
-iron
-steel
-cobalt
properties of soft magnetic materials
-soft means it loses its induced magnetism quickly
-hard means it keeps its induced magnetism permanently
