Resistor – 저항
A resistor is a two-terminal electrical or electronic component that resists an electric current by producing a voltage drop between its terminals in accordance with Ohm’s law.: The electrical resistance is equal to the voltage drop across the resistor dividedby the current through the resistor. Resistors are used as part of electrical networks and electronic circuits.
The Ideal resistor
The SI unit of electrical resistance is the ohm (Ω). A component has a resistance of 1 Ω if a voltage of 1 volt across the component results in a current of 1 ampere, or amp, which is equivalent to a flow of one coulomb of electrical charge (approximately 6.241506 × 1018 electrons) per second. The multiples kiloohm (1 kΩ = 1000 Ω) and megaohm (1 MΩ = 106 Ω) are also commonly used. In an ideal resistor, the resistance remains constant regardless of the applied voltage or current through the device or the rate of change of the current. Whereas real resistors cannot attain this goal, they are designed to present little variation in electrical resistance when subjected to these changes, or to changing temperature and other environmental factors.
Four-band axial resistors
Four-band identification is the most commonly used color coding scheme on all resistors. It consists of four colored bands that are painted around the body of the resistor. The scheme is simple: The first two numbers are the first two significant digits of the resistance value, the third is a multiplier, and the fourth is the tolerance of the value. Each color corresponds to a certain number, shown in the chart below. The tolerance for a 4-band resistor will be 2%, 5%, or 10%. The Standard EIA Color Code Table per EIA-RS-279 is as follows:
|Color||1st band||2nd band||3rd band (multiplier)||4th band (tolerance)||Temp. Coefficient|
|Brown||1||1||×101||±1% (F)||100 ppm|
|Red||2||2||×102||±2% (G)||50 ppm|
Note: red to violet are the colors of the rainbow where red is low energy and violet is higher energy. Resistors use specific values, which are determined by their tolerance. These values repeat for every exponent; 6.8, 68, 680, and so forth. This is useful because the digits, and hence the first two or three stripes, will always be similar patterns of colors, which make them easier to recognize.
5-band axial resistors
5-band identification is used for higher tolerance resistors (1%, 0.5%, 0.25%, 0.1%), to notate the extra digit. The first three bands represent the significant digits, the fourth is the multiplier, and the fifth is the tolerance. 5-band standard tolerance resistors are sometimes encountered, generally on older or specialized resistors. They can be identified by noting a standard tolerance color in the 4th band. The 5th band in this case is the temperature coefficient.