Resistor
>> Rabu, 03 Desember 2008
Resistor
A resistor is a two-terminal electronic component designed to oppose an electric current by producing a voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm's law: V = IR. The resistance R is equal to the voltage drop V across the resistor divided by the current I through the resistor.
Resistors are characterized primarily by their resistance and the power they can dissipate. Other characteristics include temperature coefficient, noise, and inductance. Practical resistors can be made of resistive wire, and various compounds and films, and they can be integrated into hybrid and printed circuits. Size, and position of leads are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power. Variable resistors, adjustable by changing the position of a tapping on the resistive element, and resistors with a movable tap ("potentiometers"), either adjustable by the user of equipment or contained within, are also used.
Resistors are used as part of electrical networks and electronic circuits.
There are special types of resistor whose resistance varies with various quantities, most of which have names, and articles, of their own: the resistance of thermistors varies greatly with temperature, whether external or due to dissipation, so they can be used for temperature or current sensing; metal oxide varistors drop to a very low resistance when a high voltage is applied, making them suitable for over-voltage protection; the resistance of a strain gauge varies with mechanical load; the resistance of photoresistors varies with illumination; the resistance of a Quantum Tunnelling Composite can vary by a factor of 1012 with mechanical pressure applied; and so on.
A resistor is a two-terminal electronic component designed to oppose an electric current by producing a voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm's law: V = IR. The resistance R is equal to the voltage drop V across the resistor divided by the current I through the resistor.
Resistors are characterized primarily by their resistance and the power they can dissipate. Other characteristics include temperature coefficient, noise, and inductance. Practical resistors can be made of resistive wire, and various compounds and films, and they can be integrated into hybrid and printed circuits. Size, and position of leads are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power. Variable resistors, adjustable by changing the position of a tapping on the resistive element, and resistors with a movable tap ("potentiometers"), either adjustable by the user of equipment or contained within, are also used.
Resistors are used as part of electrical networks and electronic circuits.
There are special types of resistor whose resistance varies with various quantities, most of which have names, and articles, of their own: the resistance of thermistors varies greatly with temperature, whether external or due to dissipation, so they can be used for temperature or current sensing; metal oxide varistors drop to a very low resistance when a high voltage is applied, making them suitable for over-voltage protection; the resistance of a strain gauge varies with mechanical load; the resistance of photoresistors varies with illumination; the resistance of a Quantum Tunnelling Composite can vary by a factor of 1012 with mechanical pressure applied; and so on.
UnitsThe ohm (symbol: Ω) is the SI unit of electrical resistance, named after Georg Ohm. The most commonly used multiples and submultiples in electrical and electronic usage are the milliohm, ohm, kilohm, and megohm.
On circuit diagrams the value may be written in "SI Notation" with the multiplier replacing the decimal point. So "2k5" means 2.5 kilo ohms
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