Physics gcse

• flemmings left hand rule:

  thumb = up or down

  index finger= direction of the poles so north to south

  middle finger= the direction of current
• There are two types of magnetic pole: a north (seeking) pole and a south (seeking) pole
• The poles of a magnet are the places where the magnetic forces are strongest
• Unlike (opposite) poles attract - the north pole of a magnet will attract the south pole of another magnet
• Like poles repel - a north pole will repel a north pole and a south pole will repel a south pole
• The region around a magnet, where a force acts on another magnet or magnetic material, is called the magnetic field
• The strength of the magnetic field depends on the distance from the magnet - it is strongest at the poles
• Permanent magnets produce their own magnetic field
• Induced magnets become a magnet when placed in a magnetic field, but lose their magnetism quickly when removed from the field
• The force between a permanent magnet and a magnetic material or an induced magnet is always one of attraction
• The arrows on field lines always run from north to south and show the direction of the force that would act on a north pole placed at that point
• The density of the field lines is called the flux density and indicates the strength of the field at that point - the closer together the lines, the higher the flux density
• The higher the flux density, the stronger the field and the greater the force that would be felt by another magnet
• When a current flows in a conducting wire, a magnetic field is produced around the wire
• The direction of the magnetic field lines around a wire depends on the direction of the current and can be determined using the right hand grip method: grip the wire in your right hand, with the thumb pointing in the direction of the current
• The strength of the magnetic field around a wire depends on the size of the current and the distance from the wire
• A solenoid is formed when a wire is looped into a cylindrical coil, increasing the strength of the magnetic field and creating a strong uniform field inside the solenoid
• To further increase the field strength, an iron core can be added to the solenoid, creating an electromagnet
• The magnetic field around a solenoid has a similar shape to that around a bar magnet
• The north pole of a solenoid can be found using the right hand grip method: hold the solenoid in your right hand with your fingers following the direction the current flows, and your thumb will point to the north pole of the solenoid
• In electromagnetic devices like an electric bell, when the switch is pushed, the electromagnet is magnetized, attracting the armature which strikes the gong and breaks the circuit, then the armature springs back, completing the circuit again and remagnetizing the electromagnet, repeating as long as the button remains pushed