magnetism Flashcards
what are the only pure metals that can be turned into a magnet
iron, nickel, cobalt
do permenant magnets form their own magnetic field
yes!
how do induced magnets become magnets
when they are in a magnetic field
if a magnetic field is further away from the poles, is it stronger or weaker?
weaker
what is a magnetic field
the area around a magnet where another magnet or magnetic material (iron, nickel, cobalt and steel) feels a force.
what shows the earth’s core is magnetic
The needle of the compass is a bar magnet and points in the direction of the Earth’s magnetic field.
right hand rule
Grip the wire with your right hand, with the thumb pointing in the direction of the current.
Your fingers curled around the wire will point in the direction of the magnetic field.
what does the strength of a field depend on
the size of the current and the distance away from the wire.
is the magnetic field of the strength and direction at each point
yes
when is an electromagnet formed
when a current carrying wire is wrapped around an iron core
what causes the motor effect
The field created by the electric current interacts with the magnetic field that the wire is placed inside
what is each finger representative of in flemings left hand rule
First finger- Field
seCond- Current
thuMb- Motion (force)
what affect the force on a current carrying wire in a magnetic field
strength of magnetic field, size of current, length of wire
why does coil carrying an electrical current rotate in a magnetic field
flemings left hand rule
how does a speaker vibrate/create soundwaves
As the direction of the current changes, the direction of the magnetic field induced (brought about) in the electromagnet changes.
A stationary (not moving) magnet repeatedly attracts and repels the electromagnet.
what increases the size of the turning force
more turns on coil, higher current, magnetic field strength
how can PD be induced
adding more coils, increasing speed of movement
when an electromotive force in induced in a wire, which direction does it create a force
opposite to action that induced (motor effect)
what is a direct current
current only flows in one direction
what is alternating current
current rapidly changes direction
what is inside an alternator
rotating magnet which alternates the direction of field and a fixed coil wire
how a dynamo produces a direct current
(generator effect)
coil rotates, generates a PD in one direction.
split-ring commutator reverses direction of current every half-turn of coil, makes sure that current is always moving in same direction to keep coil rotating induced PD is largest when coil and magnetic field are parallel to each other, when coil ‘cuts’ across magnetic field at fastest rate, PD is zero when the coil is perpendicular to magnetic field, when the coil does not ‘cut’ field lines at all.
how does a microphone work
sound waves that hit microphone make a coil inside a magnet vibrate, coil vibrates at same frequency as sound wave coming in, this induces a potential difference and current in coil.
3 main parts of transformer
primary coil, secondary coil, iron core
equation for transformers
VP ÷ VS = Np ÷ Ns
does the secondary coil have more turns than the primary coil in a step up transformer
yes
does the secondary coil have more turns than the primary coil in a step down transformer
no
voltage at which electricity is generated
15,000
voltage at which electricity is transmitted over long-distances
40,000
