By the year 1827 Georg Simon ohm, a German electrician had discovered Resistance.Georg Simon Ohm noticed that different materials that are considered electrical conductive, will not allow the current to flow within their body with the same ease. The difficulty that each material had, had to do with some parameters such as the type of the material and some external factors such as the temperature or the humidity of the atmosphere. Georg Simon Ohm described this behavior and gave the name “Resistance “. He then announced ohm’s law that connects the resistance with the voltages and the current as follows:
R = V / I
The resistor is measured with Ohms as a memorial to its inventor.
- A material having 1 Ohm resistance, will allow 1 ampere of current to flow within this material when a voltage difference of 1 volt is applied to its terminals. As defined by the international electrical congress in 1893,and by united states status, it is resistance substantially equal to 109 units of resistance of the C.G.S. system of electromagnetic units and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice 14.4521 grams in mass, of a constant cross-sectional area, and the length of 106.3 centimeters. As this is defined it is called the international ohm.
- Otis Frank Boykin, an American inventor earned his first patent in 1959. He developed the wire precision resistor which enabled manufacturers to accurately designate a value of resistance for the individual piece of wire in electronic equipment. Two years later, in 1961, Boykin earned a patent for an improved version of this concept, an inexpensive and easily producible electrical resistor model with the ability to “withstand extreme accelerations and shocked and great temperature changes without change or breakage of the fine resistance wire or other detrimental effects.”
- Boykin invented a variable resistor used in guided missile parts and control unit for heart stimulators; the unit was used in the artificial heart pacemaker, a device created to produce electrical shocks to the heart to maintain a healthy heart rate.
- Nowadays several different types of resistors exist. The most used resistors are fixed value resistors, but also variable resistors are very common. The most used variable resistors are the potentiometer and rheostat. On the other hand, there is a lot of resistors that have a variable resistance that is dependent on external factors such as temperature (thermistor), light (photo resistor), voltage (varistor), or magnetic fields (magneto resistor).