p15 - electromagnetism Flashcards
define a permanent magnet
- a magnet that always has its own magnetic field
- attracts magnetic materials and can attracts or repel other magnets
define an induced magnet
- temporary magnet made by putting a suitable material into a magnetic field
- alway an attractive force
define poles in a magnet
- ends of a magnet
- names north and south based on which way on earth they’d point if suspended freely
define magnetic field
- region around a magnet where a force acts on other magnets or magnetic materials (they are 3D unlike diagrams show)
define magnetic compass
- a small bar magnet balanced on a pin so it can spin around
- point’s towards earth’s magnetic north due to earth’s magnetic field but can still be used to find direction of a magnetic field for another magnet
where are magnetic forces the strongest?
poles of a magnet because here the magnetic field lines are the most concentrated
what happens when magnets are brought together?
- a non contact force
- like poles repel
- unlike poles attract
name the 4 magentic materials
1) iron
2) cobalt
3) steel
4) nickel
how is induced magnetism quickly lost?
if the material is moved from the magnetic field that induced it
what’s the direction of the magnetic field?
north to south
define a ‘north seeking pole’?
- sometimes the north pole is referred to as this
- because it will point north on Earth if left freely suspended
how can you find direction on a magnetic field?
by using a plotting compass
which part of earth is magnetic?
- the core because a compass at the north pole would point down
what is the difference between geographic north and magnetic north?
- geographic north is a fixed point
- magnetic north is the direction that a compass needle points to as it aligns with the earth’s magnetic field (respons to changes in earths core so is not fixed)
define current
- rate of flow of charges in a circuit
- if a current if flowing in a component, electrons are flowing through it
- a wire that has a current also has an electric field
define a solenoid
a coil of wire
define an iron core
a piece of iron placed in the middle of a solenoid
define an electromagnet
a coil of wire wth an iron core
what happens when you switch the direction of the current?
the direction of the magnetic field also switches
how can you increase the strength of a magnetic field?
- increase the current
- winding wire into coils/increasing coils
- from here you can put an iron core to increase even more, this creates an electromagnet
how do you make an electromagnet stronger?
- increasing current in wire
- increasing length of wire in solenoid
what is a good example of an iron core?
- in schools an iron nail could be used
define ‘the motor effect’
a wire carrying a current creates a magnetic field. this can interact with another magnetic field, causing a force that pushes the wire at right angles.
define ‘magnetic flux density’
- a measure of the strength of a magnetic field
- number of magnetic field lines going through a set area
define an electric motor
a device that causes rotation of a coil of wire carrying a current when placed in a magnetic field
give an equation relating to magnetic flux density
F (N) = B I L
force = magnetic flux density (tesla, T) x current (A) x length (m)
how can you work out direction of force (when you know d of current and magnetic field)
- use fleming’s left hand rule
- force = thumb (both have 5 letters)
- magnetic Field = First finger
- Current = seCond finger
how do you increase the size of the force on a conductor?
- increasing the current
- increasing length of wire
- incresing magnetic field strength
what does the communtator do in the motor effect practical?
prevent wires from tangling up
