Fundamental Physics/Electronics/Resistors

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Resistor[edit | edit source]

A resistor ( ) is an electronic component that resists, restricts, or opposes the flow of electrical current.


Symbol of resistor


Construction of resistor

A piece of resistive material with electrical contacts on both ends.

where is the length of the conductor, measured in metres [m], A is the cross-section area of the conductor measured in square metres [m²] and ρ (rho) is the electrical resistivity (also called specific electrical resistance) of the material, measured in ohm-metres (Ω·m).

In This formula are constant,therefore already is constant.

Resistance[edit | edit source]


Resistance is the resistor's characteristic to resist the current flow and reduces the voltage. Resistance has symbol R measured in ohm Ω can be calculated from Ohm's law

Ohm's law


Electricity response[edit | edit source]

passive electrical component Picture Electric response
Resitor Resistor.gif DC response

AC response

Resistor Configuration[edit | edit source]

Resistors in Series[edit | edit source]

For n resitors connected adjacent to each other as shown

The total resistance

For 2 series resistor of same value

Resistors in parallel[edit | edit source]

For n resitors connected facing each other as shown

The total resistance

For 2 parallel resistor of same value

Resistors in 2 port network[edit | edit source]

2 resistor to form 2 port network as shown

3 resistor connected in T configuration

3 resistor connected in Π configuration

Resistor color code[edit | edit source]

Color Significant
Multiplier Tolerance Temp. Coefficient (ppm/K)
Black 0 ×100 250 U
Brown 1 ×101 ±1% F 100 S
Red 2 ×102 ±2% G 50 R
Orange 3 ×103 15 P
Yellow 4 ×104 (±5%) 25 Q
Green 5 ×105 ±0.5% D 20 Z
Blue 6 ×106 ±0.25% C 10 Z
Violet 7 ×107 ±0.1% B 5 M
Gray 8 ×108 ±0.05% (±10%) A 1 K
White 9 ×109
Gold ×10-1 ±5% J
Silver ×10-2 ±10% K
None ±20% M
  1. Any temperature coefficent not assigned its own letter shall be marked "Z", and the coefficient found in other documentation.
  2. For more information, see EN 60062.
  3. Yellow and Gray are used in high-voltage resistors to avoid metal particles in the lacquer.

4-Band Resistor.svg

Resistors found in electronic kits and hobby projects have up to four bars indicating the color code. The first two bars represent the first and second significant digit, the third represents the exponent or decimal multiplier, and the fourth represents the tolerance. The chart to the right shows information about the color coding on resistors.

Further Reading[edit | edit source]

External Links[edit | edit source]