![]() ![]() Resistor Color Code What is Tolerance of a Resistor? I use the Euro version of the symbol exclusively. ![]() The schematic symbols for resistors are either of those shown below. The letter “ R” and the “ 2k2” conventions are European, and not commonly seen in the US and other backward countries □ Other variants are 0R1, for example, which means 0.1 Ohm. The use of the symbol for Ohms ( Omega, Ω) is optional, and is most commonly left off, since it is irksome to add from most keyboards. To explain – a resistor has a value of 2,200 Ohms. There are a few conventions that are followed, and these can cause problems for the beginner. Resistor values are often stated as “ k” ( kilo, or times 1,000) or “ M“, ( meg, or times 1,000,000) for convenience. The resistance value is specified in ohms, the standard symbol is “ R” or Ω. The value of a resistor is measured in ohms and represented by the Greek letter capital omega ( Ω). This type of resistor makes an excellent light sensor. When the photocell is exposed to more light, the resistance decreases. The photo resistor or photocell is composed of a light sensitive material. The resistance between the two stationary contacts is, of course, fixed, and is the value specified for the potentiometer. Potentiometers generally have three terminals, a common slider terminal, and one that exhibits increasing resistance and one that has decreasing resistance relative to the slider as the shaft is turned in one direction. When the knob of a potentiometer is turned, a slider moves along the resistance element. What is a Potentiometer?Ī potentiometer is a variable resistor. There are non-inductive Wirewound resistors, but are not readily available, and usually not cheap. Resistors may also have inductance, and Wirewound types are the worst for this. ![]() Low noise circuits will always use low resistor values and low voltage wherever possible. Noise is proportional to temperature and voltage. Everything that is above 0K ( zero Kelvin, absolute zero, or -273 degrees Celsius) makes noise, and resistors are no exception. Acceptable to very good tolerance, good stability. Comparatively poor tolerance and stability. Rather, we use small pipes, valves, and other devices to limit water flow to practical levels. Water mains and fire hoses have their uses, but you do not want to take a drink from one. If you think of current, charge flow, in terms of water flow, a good electrical conductor is like big water pipe. We need some way to control the flow of current from a voltage source, like a battery, so we do not melt wires and blow up batteries. It is a passive device used to control, or impede the flow of, electric current in an electric circuit by providing resistance, thereby developing a drop in voltage across the device.
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