Electromagnetism Flashcards
What are the magnetic metals?
Iron
Cobalt
Nickel
Steel
Permanent magnet
Always causes a force on other magnets or on magnetic materials
Key features of a permanent magnet
Produces own magnetic field
Magnetic field lasts forever
Usually made of steel
Induced magnet
Only becomes a magnet when it is placed in a magnetic field
How to plot a magnetic field?
Place the magnet in the middle of the page and draw around it with a pencil
Place a compass by the north end and place a dot where the red point come to rest
Remove the compass and place it on the dot you have just made. The tail should be on the dot
Repeat this process until the dot returns to the magnet
Repeat at different starting points
Put arrows on the field lines to show the direction
Electromagnet
Can turn on and off the magnetism
Electromagnet used in
High speed trains
MRI machines
Junkyard canes
How to make a field stronger
Increase current
Increase number of turns in the coil
Add an iron core
What does the thumb represent?
Force
What does the pointer finger represent?
Magnetic field
What does the middle finger represent?
Direction of current
How to change direction of force on a wire
Reverse the direction of the current
Reverse the direction of the magnetic field
What does the split ring commutator do
Reverses the direction of the current every half turn of the coil
What do graphite brushes do
Connect the split ring commutator to a power source
Why use graphite
Conducts electricity
Very slippery so little energy is wasted due to friction
