area around a magnet where the magnetic force acts
What are substances that can be permanently magnetised described as?
magnetically hard
Give 3 examples of things that are magnetically hard?
alloys like iron, nickel and cobalt
Definition of magnetically hard?
substances that can be permanently magnetised
Definition of magnetically soft?
substances that can only be temporarily magnetised
What are alloys with iron called?
ferrous
How to draw a field around a bar magnet?
increasing in distance between lines
Where do the magnetic field lines always point towards?
south
Draw the field around two magnets with unlike poles facing?
lines must be straight
Draw the field around two bar magnets with like poles facing each other?
repulsion
How do we set up a uniform magnetic field?
opposite poles facing, magnetsclose enough for there to be a field, nottooclose for there to be attraction
What do we mean if we say the magnetic field is uniform?
lines are equal distant away
How can we make an electromagnetic?
by putting current through a wire
What are the positives of electromagnets?
temporary so can be turned on and off with a switch
What three ways make a magnet stronger?
more turns on coil, morecurrent, use an iron core
What does it mean if the circle in the middle of a wire is shaded in?
current towards you
What does it mean if the circle in the middle of a wire has a cross?
current moves away from you
What hand rule do we use to decide what way the field goes if given current?
right hand thumb rule
How does the right hand thumb rule work?
depending on centre of wire, point thumb away or towards you and follow knuckle round to nail either anticlockwise or clockwise
How do you draw a field around a solenoid?
like a bar magnet with north to south
What is the motor effect?
currentmoves through coil to make the electromagnetic field, the electromagnetic fieldinteracts with the permanentmagneticfield which causes a force which causes movement
How does the motor work?
every half turn the split ringcommutatorreverses the current in the coil
How can you change the direction of the movement of wire?
change current direction or polarity of magnet
What happens to the direction of movement of wire if you change both the current direction and polarity of manet?
wire moves in original direction
How would you increase the speed of the wire?
increasevoltage, make wire into coil or make permanentmagneticfieldstronger
How does increasing voltage increase the speed of wire?
makes electromagnetic field stronger which increasesinteractionbetweenfields so moreforce
How does making the wire into a coil increase the speed of wire?
make the electromagnetic fieldstronger with increasesinteractionbetweenfields so moreforce
How does making the permanent magnet stronger increase the speed of wire?
makes electromagnetic field stronger so increases interaction meaning more force
What might happen if the wire was parallel to the field?
nointeraction so nomovement so noforce
State and explain three methods that the induced voltage and current can be increased?
move the wirequickly which cuts through moremagneticfieldlines, use strongermagnet so morefieldlines to cut, wrap wire into a coil so morepieces of wiremoving
What happens during electromagnetic induction if you move the wire?
it cuts through the magneticfield so a voltage is induced
What happens during electromagnetic induction if you move the magnet?
induces a voltage
What is faraday's law of electromagnetic induction?
the size of induced voltage across ends of a wire is directly proportional to rate at which the magneticfieldlines are being cut
how to make electricity via induction?
coil of wire cuts through permanentmagneticfield which inducesvoltage
How does the AC generator work?
the rectangularcoil spins in magnetic field, as it spins it cuts through field lines, the frequency of alternating current is number of cycles per second
What does the alternating current mean in a generator?
the current is the number of complete cycles per second
Explain the meaning of 50Hz of alternating current?
currentconstantlychangesdirection50 times back and forthpersecond
Explain why there is an alternating current?
so the current constantly moves back and forth so moves quicker allowing move magnetic field lines to be cut so move voltage is induced
What happens to voltage if more magnetic field lines are cut?
more voltage is induced
How does a loudspeaker work?
alternating current flows through coil and makes electromagnetic field, this interacts with the permanent magnetic field which cause force so causes movement making a vibration of 100 times per second of a longitudional wave