Electromagnetism / Magnetism Flashcards
______ hand generator rule
right hand generator rule
_____ hand motor rule
left hand motor rule
what does each finger do in Flemming’s rule?
Thumb = motion of force
FIrst FInger = magnetic field
seCond = current
What does a split ring commutator do?
It reverses the direction of current flow each half turn causing alternating current (AC)
What are lines of flux?
magnetic Field Lines
Magnetic metals 4x
nickel, iron, steel, cobalt
What is electromagnetic induction?
The creation of emf due to a magnet passing an electromagnet.
What is trhe motor effect?
When the current in a wire is in presence of a magnetic field a force is produced
What is the generator effect?
When a wire moves across lines of flux, causing emf to be induced and therefore a current to flow.
How do you find the poles of an electromagnet?
Right hand grip rule. thumb = north. fingers curl in direction of current
What is a solenoid
a COIL OF WIRE.
Whats the purpose of brushes in a motor and generator?
Used in a SRC to enable a continuous connection = constant current flow.
What’s the purpose of brushes in a motor and generator?
To avoid sparks caused by current flow.
What happens to domains in a magnetised material?
The material gains poles, arrows point in the same direction (N-S), temporary magnetic field and therefore a temporarily induced magnet.
Current in circuit, + to - or - to +
+ to -
What is a transformer?
2 coils wrapped around a soft iron core that is used to transform voltages.
How can you increase the voltage in a generator? x4
(aka increase lines of flux crossed per unit time)
inc magnetic force of magnet
inc no. coil turns
inc rotation speed
inc wire length
What is a DC motor?
A coil of wire inbetween 2 permenant magnets causing current to flow = turning effect occurs
3x ways to increase strength of magnetic field
inc current
inc coils in electromagnet
inc magnet strength
How can you induce a magnet?
in a coil with direct current or hammering it
how can you demagnetise a material?
heating, hammering or put it in a coil with an AC.
Practical for electromagnet induction explain.
electromagnet and milli voltmeter in series
drop magnet through centre of coil. Causing increase of V on millivoltmeter.
How can you show the lines of flux? (practical)
Using iron filings or using compasses
transformer equation
Vp/ Vs = np/ns
[n = turns of coil]
current and voltage transformer equation
Ip x Vp = Is x Vs
Does a transformer use AC or DC
AC
What do brushes do on a split ring commutator?
Passes the current onto the SRC
What is a step down transformer?
When voltages are transformed from high to low
How can you demagnetise a magnet
Put into AC coil and withdraw slowly
Hammer it when not in a field
Heat it and leave it to cool
