The role and development of resistance

Low-power resistors are usually composed of carbon films encapsulated in a plastic housing, while high-power resistors are usually wire wound resistors, made by winding a high-resistivity metal wire around a porcelain heart.

If the resistance value of a resistor is close to zero ohms (for example, a large cross-section wire between two points), the resistor has no hindering effect on the current, and the circuit in parallel with such a resistor is short-circuited, and the current is infinite. If a resistor has an infinite or large resistance, the circuit connected to the resistor can be regarded as open and the current is zero. Resistors commonly used in industry are between the two extreme cases, it has a certain resistance, can pass a certain current, but the current is not as large as when the short circuit. The current limiting effect of a resistor is similar to that of a small diameter pipe connected between two large diameter pipes to limit the flow of water. resistance, the English name resistance, is usually abbreviated to R, which is a basic property of conductors, and is related to the size, material and temperature of conductors. Ohm's law says that I=U/R, then R=U/I, and the basic unit of resistance is the ohm, which is indicated by the Greek letter "Ω".

There is such a definition: when a voltage is applied to a conductor, the resistance value corresponding to an ampere current is generated. The main function of resistance is to prevent the flow of current. In fact, "resistance" refers to a property, and the resistance usually referred to in electronic products refers to such a component as a resistor. Ohm is often shortened to Ohm. The common units that indicate the resistance value are also thousand ohm (kΩ), megohm (MΩ), milliohm (mΩ).

develop

1885 British C. Bradley invented molded carbon solid core resistor

Bell Laboratories

In 1897, the British T. Gambrill and A. Harris made carbon film resistors with carbon ink. 1913~1919 British W. Swan and German F. Kruger successively invented metal film resistor. In 1925, Germany's Siemens-Halske company invented the thermal decomposition carbon film resistor, which broke the monopoly market situation of carbon solid core resistor. After the advent of transistors, the requirements for miniaturization of resistors and stability of resistance values are stricter, which promotes the development of various new resistors. The TaN resistor was developed by Bell Laboratories in 1959. Since the 1960s, the use of drum magnetron sputtering, laser resistance value fine-tuning and other new processes, some products to planarization, integration, miniaturization and flaky development.