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CHAPTER 2 - RESISTORS
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RESISTORS’ ATTRIBUTES
- Resistance named value: the value written on the body of the resistor in Ω.
- Named power: the maximum thermal power the resistor can produce towards the environment, without getting destroyed; yet, is provided in a diagram by the manufacturer, in connection with the environment temperature. This is provided in Watts and specifies generally the dimensions of the resistor. Some standard power values are 1/8, 1/4, 1/3, 1/2, 3/4, 1, 2, 3, 4, 6, 7, 8, 10 etc. Watts.
- Resistance tolerance: the % change of the named value and is provided as ±A%. The standardized values of tolerance are for every each series the following: E3 and E6 ±20%, E12 ±10%, E24 ±5%, E48 ±2%, E96 ±1% and E192 ±0.1% or ±25% or ±0.5%. The series E192 for resistors of very high accuracy has also the tolerance values ±0.01%, ±0.02% or 0.05%.
- Maximum operation voltage: that which causes the loss of warmth, as much as the named value of power and is provided by the following equation:
- Voltage factor: the value expressing the change in the value of resistance, according to the voltage applied in its ends and is provided in ppm/V. this change is expressed approximately by this equation:where RU is the resistance in voltage U, R0 and U0 are the resistance and the reference voltage respectively and kU is the voltage factor of the resistance, in ppm/V.
- Temperature coefficient, in ppm/°C.
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