Magnetism Flashcards
A magnet is any material or object that produces what
A magnetic field
What all magnets have in common is that they have … poles and they’re surrounded by a…
2 (North and south)
Magnetic field
Direction field lines should be drawn
North to south
More dense field lines (magnetic field lines drawn closer together) means what
The stronger the magnet
How to represent a stronger magnet with magnetic field lines
Field lines are more dense (drawn closer together)
Does the compass needle point to the north or South Pole of the magnet
South
(Opposite of what you might think as magnetic south is geographical north)
3 examples of magnets
The earth
Bar magnet
Horse shoe magnet
3 magnetic metals
Cobalt
Nickel
Iron
(Also steel as it’s an alloy of iron)
A permenant magnet produces its own what all the time
Magnetic field
Induced magnets only become magnetic when placed in what
A magnetic field
(They don’t produce their own magnetic field)
Permanent vs induced magnet
Permanent= object that produces its own magnetic field all the time
Induced= Only becomes temporarily magnetic when placed inside a magnetic field so doesn’t produce its own magnetic field
The force between a permenant and induced magnet will always be what
Attractive
Electromagnetism is where lecturing currents produce their own what
Magnetic fields
If current flows through the wire, the electric current will produce a magnetic field all around the wire. True or false
True
When working out which way the magnetic field lines go around current from a wire, what rule do we use
Right hand rule
(You do a thumbs up/ thumbs down/ thumbs sideways with your right hand with your thumb pointing in the direction the current is going through the wire. The way your finger curl is the way the current is going)
How to use right hand rule to work out direction of magnetic field lines for current flowing through wire
Do thumbs up/ thumbs down/ thumbs sideways with thumb pointing in direction current is flowing through wire
The way your fingers are turning/ curled is the way the magnetic field lines are going
The magnetic field within a solenoid is what 2 things
Strong
Uniform
True or false, a solenoid has a north and South Pole
True
The magnetic field lines go in one end and out one end so we’ve effectively sued electricity to create a magnet
(Hence a solenoid is an electromagnet)
When are electromagnets like solenoids magnetic
When the current is flowing as the current generates a magnetic field
How can we reverse the direction of a magnetic field on an electromagnet
Reverse direction of current
How can we reverse the direction of a magnetic field on an electromagnet
Reverse direction of current
What happens if we reverse the direction current is flowing through an electromagnet
Magnetic field lines change direction
(And the sides of the poles also switch around)
Standard electromagnets only produce a very small magnetic field.
What are 3 ways we can make the magnetic field stronger
Increase current
Increase number of turns in coil /length of solenoid still stays the same)
Add iron core inside solenoid
What is the motor effect
When a conductor carrying current is placed in a magnetic field, the magnet producing the field and the conductor exert a force on each other
What happens if a wire carrying a current is placed between 2 magnets
Seeing as both the current and the 2 magnets produce their own magnetic field, the magnetic fields will interact meaning there is then a force on the wire
(Wire must be 90 degrees to magnetic field lines of magnet)
How to use Flemings left hand rule to work out direction of force on wire
Thumb= force
First finger= magnetic field line
Second finger= current
Line fingers/ thumb up with information you already have- they should all be at right angles to each other
The wire must be at what angle to the magnetic field to accurately be abl to calculate strength of force in motor effect
90 degrees
What does F= B x I x L stand for
Force= magnetic flux density x current x length of wire
What is magnetic flux density
Magnetic field strength
(More dense field lines= lines closer together= stronger)
For an electric motor what’s used to ensure the coil keeps turning in the same direction
Split ring commutator
What is a magnetic field
The region around a magnet where another magnet or magnetic material will experience a force due to the magnet
What shape are magnetic field lines around the current flowing through a wire
Concentric circles
Why does a solenoid (coil of wire) instead of just a single straight pice of wire have a stronger mange tic field strength
The small magnetic fields caused by the current in each coil add together to make a stronger overall magnetic field
How does an electric motor spin
A current in the Clío induces a magnetic field
This magnetic field interacts with the magnetic fields of the magnets either side
This interaction of the 2 magnetic fields creates an upward force on one side of the coil and a downward force on the other side (as the current is going in a different direction on each side) which makes the coil spin
When the coil rotates past the vertical position the split ring commutator reversed the direction of the current in the coil
This keeps the motor turning
For the generator effect what makes a potential difference be induced (created) across each end of the conductor
The conductor is moving relative to the magnetic field
(Wire must be moving up and down to cut through magnetic field lines)
When will a current flow in the generator effect
If the conductor is part of a full circuit
For generator effect 3 ways to increase PD induced
Stronger magnet
More turns in coil
Move coil quicker
