P4.1 Flashcards
Two types of forces
Contact or non-contact
What is a magnet
A magnet is any object that has magnetic field around it.
The Closer the field lines…
The stronger the magnet
What is a permanent magnet
A permanent magnet is one which always has amagnetic field around it.
What happens when a non magnet is brought close to a magnet
The non-magnets have magnetism induced in them when the permanent magnet is brought close.i.e. a non magnetic material can sometimes be temporarily made magnetic, and thus will attract (repel) other permanent magnets.
Direction of magnetic field lines
Magnetic field lines go from the North pole to the South pole of a magnet.
do field lines cross
NO NEVER THATS WRONG OMG
What is a magnetic field
A region of space within which magnets and magnetic materials experience a magnetic force of attraction or repulsion.
What happens when current flows in a wire
A magnetic field is created around it
What do the magnetic field lines around a current carrying wire look like
Like concentric rings
How do you work out direction of magnetic field lines
Corkscrew rule - RIGHT HAND ONLY
What is a solenoid
A solenoid is a device that acts to increase the strength/size of the magnetic field around a current carrying wire.
Solenoids are used to produced what type of magnet
Electromagnet
How is a solenoid made
A wire is looped many times around a piece of metal (not a magnet!) that can be magnetised (iron which is magnetic material)
What is an electromagnet
A magnet which runs on electricity (electric current).
An electromagnet’s magnetic field can be switched on and off, by switching the current on and off.
Factors that effect electromagnets
- The number of coils in the wire.
- The size of the current through the wire.
- Changing the material of the core inside the coils.
Magnetic metals
Iron
Cobalt
Nickel
two types of magnets
Permanent magnets
Induced magnets
Permanent Magnets
made out of permanent magnetic materials, for example steel
will produce its own magnetic field
It will not lose its magnetism
Examples of permanent magnetic material
Steel
Induced Magnets
When a magnetic material is placed in a magnetic field, the material can temporarily be turned into a magnet
Special about induced magnetism
Magnetic materials will always be attracted to a permanent magnet - ALWAYS HAVE OPPOSITE POLE to magnets closest pole
When the induced magnetic material is removed from the magnetic field…
lose most/all of its magnetism quickly
Earth
Factors Affecting Magnetic Field Strength
The size of the current
The distance from the long straight conductor (such as a wire)
How to find the polarity of each end on the solenoid
If the current is travelling around in a clockwise direction then it is the South Pole
If the current is travelling around in an anticlockwise direction then it is the North Pole
To increase strength of solenoid - add core of what
Iron
Why iron
The iron core will become an induced magnet when current is flowing through the coils
The magnetic field produced from the solenoid and the iron core will create a much stronger magnet overall
What is a soft magnetic material
easy to magnetise but also easily lose their magnetisation.
Example of a soft magnetic material
Iron
What is a hard magnetic material
difficult to magnetise but once they are magnetised, they are difficult to demagnetise.
Example of a hard magnetic material
Steel
Uses of soft magnetic material
Electromagnets - turn on and off quickly (iron core)
Uses of soft magnetic material
Permanent Magnets
What is an electromagnet
consists of a long coil or solenoid wound around a core made from a soft magnetic material such as iron.
Differences between electromagnet + permanent magnet
The core of an electromagnet is made from a soft magnetic material. Why would a hard magnetic material be unsuitable for this purpose?
Hard magnetic materials are difficult to magnetise so they would not create a strong magnetic field when the current is switched on. Once magnetised, they retain their magnetisation so it would not be possible to switch the electromagnet off.
Why is there a limit to how much current you can put through an electromagnet
results in a strong heating effect that could melt the insulation - use a superconducting coil (coils of zero resistance)
