P15

• Motor effect is the force that can act on a wire in a magnetic field when a current is passed through the wire
• Size of force from motor effect can be increased by increasing current and using stronger magnet
• Size of force from motor effect will be greatest when the wire is perpendicular to the magnetic field
• the direction of force from motor effect is always at right angles to the wires and field lines
• In fleming's left hand rule, thumb shows movement
• In fleming's left hand rule, first finger shows field
• in fleming's left hand rule, second finger shows current
• magnetic flex denisty of a magnetic filed is the measure of the strength of the magnetic field.
• Split ring commutator swaps the positive and negative connections
• Electromagnetic induction is when a potential difference is created as a genertor containg coils of wires that spin in a magnetic field crosses through the magnetic field lines
• The generator effect is the effect if conductor is part of complete circuit it will cause the induced pd to make an electric current pass through the circuit
• In electromagnetic induction, the pd wont be created if the wire is stationary
• Potential difference created by generator effect will also generate current thru the coil/wire
• if there is opposite movement of coil or magnet in generator effect, the potential difference will act in opposite direction
• Solenoid is a long coil of insulated wire. Solenoids are used in lots of devices where a strong magnetic field needs to be prodcued.
• An electromagnet is a solenoid in which the insulated wire is wrapped around an iron core. When currents passes through wire, it magnetises iron bar and when current is switched off the iron core loses its magnetism
• resistance is inversely proportional to square of current
• Reversing direction of current in solenoid reverses direction of magnetic field
• Increasing current in solenoid increases strength of magnetic field
• in motor effect when the wire is at 90º to magnetic field the force is maximum
• in motor effect if wire is parallel to magnetic field the force is 0
• size of induced pd is increased in generator effect by increasing: speed of movement, strength of magnetic field, number of turns on coil