MAGNETISM + ELECTROMAGNETISM Flashcards
what is induction?
when a wire passes through a magnetic field line and voltage is induced
magnetic materials:
- iron
- cobalt
- nickel
how is magnetism induced in some materials?
when they are placed into a magnetic field
what are magnetic field lines?
show the direction that a magnet would point
what direction do magnetic field lines go from?
North to South
can magnetic field lines cross?
no
what is an electromagnet?
any current carrying wire
P2 how are electromagnets made ?
by winding coils of wire, you can turn them on and off
how to increase the strength of a magnetic field?
- wind more coils
- insert a magnetic core
- use a higher current
how to use two magnets to produce a magnetic field around them:
North Pole facing South Pole
P2 what is there on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field?
a force
what are the properties of a magnetically hard material?
hard to magnetise but retains magnetism better
what are the properties of a magnetically soft material?
easy to magnetise but lose magnetism easily
why is a force exerted on a current-carrying wire in a magnetic field in simple d.c. electric motors ?
- Current flows in the wire/coil.
- This creates a magnetic field around the wire/coil.
- This magnetic field interacts with the field from the permanent magnet.
- This produces a force on the wire/coil which moves the wire/coil.
- The split-ring communicator changes the direction of the current every half turn as it spins.
- This reverses the direction of the forces, allowing the coil to continue spinning.
why is a force is exerted on a current-carrying wire in a magnetic field in simple a.c. loudspeakers?
- An alternating current from the source passes though the coils in the speaker.
- This current is constantly changing direction and magnitude
- This current creates a magnetic field around the coil
- This field interacts with the magnetic field from the permanent magnets
- Creating a constantly changing force on the coil.
- This causes the coil to vibrate in and out as the direction of the force changes, moving the cone
- The cone causes vibrations which we hear as sound waves.
what does the first finger represent in FLHR?
magnetic field direction
what does the middle finger represent in FLHR?
direction of current
what does the thumb represent in FLHR?
direction of force
how does the force on a current-carrying conductor in a magnetic field change with the magnitude and direction of the field and current?
- If you increase the magnitude of the current through a wire or the size of the magnet being used, you increase the force on the wire.
- If you change the direction of the current or reverse the poles of the magnet, you change the direction of the force on the wire
when is voltage induced in a current or coil?
when it moves through a magnetic field or when a magnetic field changed through it
how can you induce a voltage?
changing the strength of a magnetic field
factors affecting current:
- strength of the magnetic field
- increase the numbers of wire being cut (use coils rather than a single wire)
- increase the speed of the movement or rotation of the wire and magnetic field relative to eachother
how do we generate electricity?
rotating a magnet within a coil of wire and of a coil of wire within a magnetic field
P2 describe the structure of a transformer:
- work by passing a magnetic field between two coils
- primary coil creates an alternating magnetic field (as it is connected to AC supply)
- the alternating magnetic field passes around inside the transformer’s core
- the alternating magnetic field creates a voltage in the secondary coil
