Magnetism and Electromagnetism Flashcards
(36 cards)
What do magnets do?
Magnets repel and attract other magnets and attract magnetic materials.
What happens when like poles of magnets are brought together?
Like poles repel.
What happens when opposite poles of magnets are brought together?
Opposite poles attract.
Define non-magnetic materials.
Materials that are not attracted to magnets and cannot be magnetised (e.g. glass, plastic).
Define magnetic materials.
Materials that are attracted to magnets and can be magnetised (e.g. iron, steel, cobalt, nickel).
How can magnetism be induced in magnetic materials?
By placing them in a magnetic field.
What are magnetically hard materials?
Magnetic materials that can be permanently magnetised (e.g. steel).
What are magnetically soft materials?
Magnetic materials that are only temporarily magnetised (e.g. soft iron).
What occurs in bulk material regarding magnetic domains?
The domains usually cancel, leaving the material unmagnetized.
What do magnetic field lines represent?
The magnetic force on a north pole at a given point.
What does the direction of a magnetic field line indicate?
The direction of the force.
What does the spacing of magnetic field lines indicate?
The magnitude of the force.
From where to where do field lines from magnets point?
From north to south.
Describe the uniform magnetic field between two magnets.
Field lines move from the north pole of one straight towards the south pole of the other, are parallel and evenly spaced.
What does an electric current passing through a conductor produce?
A magnetic field around it.
What is the motor effect?
The phenomenon where the direction of force, field, and current determines movement.
What happens if the current or magnetic field is reversed in a motor?
The force will be reversed.
How does increasing the magnitude of the current or magnetic field affect the force?
The magnitude of the force will increase.
What are the main components of a DC motor?
A coil of wire, two permanent magnets, and a split ring commutator.
What does a DC motor do when direct current flows through the wire?
It experiences a turning effect due to forces exerted in the magnetic field.
How can the turning effect in a DC motor be increased?
By:
* Increasing the current
* Using a stronger magnetic field
* Increasing the number of turns on the coil.
What is the function of a split ring commutator in a DC motor?
To ensure that the direction of current flow in the coil reverses every half turn.
How do loudspeakers produce sound?
By using a coil attached to a cone in a magnetic field with alternating current.
What effect does changing the frequency of alternating current have on sound produced by a loudspeaker?
It alters the frequency and therefore pitch of the sound.
