Having said that, Georg Ohm came up with an equation that explains this relationship: where ρ = resistivity (Ω-m) On the other hand, resistance decreases as the thickness of wires increases. This means that the longer and thinner wires offer more resistance. He proved that the resistance (R) of a material increases as its length increases. George Ohm studied the relationship between resistance and the size of the material that was used to make the resistor. As we’ve found out, it’s easier for the electrons to flow in some conductor materials than insulators. The thinner the copper, the higher the resistance since it’s harder for the electrons to pass through it. Resistance depends on those copper turns. However, if you break it open, you’ll see an insulating ceramic rod running through the middle with copper wire wrapped around the outside. If you look at resistors from the outside, they most likely look the same. Wiring a resistor in a circuit will reduce the current by a precise amount. Examples of this are potentiometers, rheostats, trimmers, and so on. The slider taps onto the main resistor element so there will be three connections two are connected to the third element and one to the slider.
Variable resistors have fixed resistor elements plus a slider. It can also be made with a mixture of finely ground carbon or be very small in size and for high power rating. It can have a carbon composition or chip-and-wire wound type. Their values should never be changed to adjust the circuit since those were determined during the design phase. Fixed resistors are designed to set the right conditions in a circuit.