Resistors are essential components in electronic circuits and play an important role in controlling and limiting the flow of current. They can be divided into different categories based on power requirements and application type. For example, common in low-power applications are carbon film resistors, which are often encased in a plastic housing. In contrast, high-power applications mostly use wirewound resistors, which are made of high-resistivity metal wire wound on a ceramic core.
The basic function of a resistor is to create an obstruction to the flow of electrical current. When the resistance value of the resistor is close to zero ohms, such as between two points connected by a large cross-section wire, its blocking effect on the current is almost non-existent. At this time, the circuit is equivalent to a short circuit and the flow of current is almost unrestricted. On the contrary, when a resistor has an extremely large resistance value, the resistor in series with the circuit will cause the circuit to become an open circuit and current will not flow. Resistors in practical applications usually fall somewhere between these two extremes. They have a resistance value that allows a certain amount of current to pass through, but does not allow the current to reach the level of a short circuit. The current limiting effect of a resistor can be compared to the situation where a small diameter pipe connected between two large diameter pipes restricts the flow of water.
The English name of resistor is resistance, usually abbreviated as R. It is a basic property of the conductor and is related to the size, material and temperature of the conductor. According to Ohm's Law, the relationship between current I, voltage U and resistance R can be expressed as I=U/R, so R=U/I. The unit of resistance is ohms, represented by the Greek letter "Ω". The resistance of a conductor when a voltage of one volt is applied to produce a current of one ampere is defined as one ohm. The main function of a resistor is to hinder the flow of current. In electronics, a resistor refers to a component of this nature. In addition to the basic unit ohm, resistance values are expressed in kiloohms (kΩ), megaohms (MΩ) and milliohms (mΩ).
The history of resistors dates back to the late 19th century. In 1897, T. Gambrill and A. Harris in the UK made a carbon film resistor using carbon-containing ink. In the early 20th century, resistor technology made significant advances. From 1913 to 1919, W. Swann of the United Kingdom and F. Kruger of Germany invented metal film resistors respectively. In 1925, the German Siemens-Halske Company invented the thermal decomposition carbon film resistor, ending the monopoly of carbon solid core resistors on the market. With the advent of transistors, the requirements for miniaturization and resistance stability of resistors have become more stringent, promoting the development of various new types of resistors. In 1959, Bell Labs in the United States developed the TaN resistor. Since the 1960s, the manufacturing process of resistors has experienced the application of various new technologies such as drum magnetron sputtering and laser resistance trimming, which has led to the development of some resistor products in the direction of planarization, integration, miniaturization and flakes.