what you're looking at is a very simple alternating current or ac generator a device that converts mechanical energy into electrical energy this part is called the armature it's made from metal and electricity is generated by its rotation between two magnets to show clearly how the generator works one half has been colored yellow the armature can be rotated in various ways for example using pressurized steam as in a power plant a flow of water from a dam or a flow of air from a wind turbine these parts are called slip rings they're also made of metal and are connected to the armature the slip rings and the armature rotate together the rings are connected to brushes made from carbon the brushes make contact with the rings as the rings rotate so they provide an electron flow within the system in order to determine the magnitude and direction of current a galvanometer is attached when the armature starts to rotate an electric current is formed this is because the magnetic flux changes over time magnetic flux is a measurement of the total magnetic field that passes through a surface notice that electric current is formed not because of the magnetic flux but because of a change of flux magnetic flux might be non-zero but if the rate of change of the flux is zero there won't be a current formation of electric current depends on the change of flux which can be calculated by this formula if the angle between the area vector and the magnetic field is zero the rate of change of the flux is zero when the armature is parallel to the magnets the rate of change of flux is zero so that no electricity is generated but as the armature rotates the magnetic flux starts to change electrons in the armature start to flow and an electric current is formed after a quarter of a cycle the change of the magnetic flux reaches a maximum and so the current reaches a maximum two as the armature continues to rotate the change of the magnetic flux gradually decreases and consequently the current decreases as well when the yellow armature part reaches the bottom the armature is parallel to the magnets and because the change of magnetic flux is zero at this point the current is zero as well up to this stage according to fleming's right hand rule the current's direction is inward as the armature keeps rotating the magnetic flux starts to change again and reaches its maximum when the yellow armature part approaches the magnet as the armature rotates further the change of the magnetic flux decreases until it becomes zero and the cycle is completed between half and complete cycle fleming's right hand rule indicates that the direction of current is outward so every quarter cycle the electric current reaches a maximum and every half cycle the current drops to zero after every half cycle the direction of the current changes this change of the direction of the current is the biggest difference between alternating current and direct current in direct current in order to prevent changes of current direction only one ring known as a split ring is used in an ac generator the frequency at which the current changes direction is determined by the rotation speed for example in the united states the ac frequency is 60 hertz which means that the current changes 60 times back and forth every second whereas in europe the ac frequency is 50 hertz the choice of these frequencies dates back to the 19th century at this time efficient speeds for steam turbines to rotate were between 3000 and four thousand revolutions per minute in europe three thousand rpm generators began to be used which generate 50 hertz frequencies whereas in the us 3600 rpm generators were used which generate a frequency of 60 hertz you