# Resistor

A Resistor is a passive two terminal electrical component that implements electrical resistance as a circuit element. In electronics circuits, resistors often used to limit current flow, to adjust signal levels, bias active elements, and terminate transmission lines among other uses.

Fixed resistors have resistance that only changes slightly with temperature, time and operating voltage.
Variable resistors can be used to adjust the circuit elements (such as volume or lamp dimmer), or as sensing devices for heat, light, humidity, force or chemical activity.

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Resistors are said to be connected in "series", when they are daisy chained in a single line. Resistors in series have a common Current flowing through them.

The total resistance, RTotal of the series resistor circuit must be equal to the sum of all the individual resistors added together. Therefore

## RTotal = R1 + R2 + ... + Rn.

The total voltage, VTotal of the series resistor circuit must be equal to the sum of all the individual voltages added together. Therefore

## VTotal = VR1 + VR2 + ... + VRn.

The current across all resistors in the series resistor circuit remains same.

## ITotal = IR2 = IR2 = ... = IRn.

Resistors are said to be connected together in "parallel", when both of their terminals respectively connected to each terminal of the other resistors. Resistors connected in parallel have common voltage across them.

The total resistance, RTotal of the parallel resistor circuit must be equal to the reciprocal sum of all the individual resistors added together. Therefore

## 1/RTotal = 1/R1 + 1/R2 + ... + 1/Rn.

The voltage across all resistors in the parallel resistor circuit remains same.

## VTotal = VR1 = VR2 = ... = VRn.

The total current, ITotal of the parallel resistor circuit must be equal to the sum of all the individual currents added together. Therefore