Fundamental Physics/Electronics/Resistors

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Resistor[edit]

Resistor.jpg

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

Symbol[edit]

OhmsLaw.svg

Resistor Construction[edit]

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

The electrical resistance of a given object depends primarily on two factors:

  • What material is it made?
  • what is shape?

therefore, can be computed as:

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.

Resistor's Resistance[edit]

OhmsLaw.svg

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

Therefore,

Resistor in DC circuit[edit]

Resistance[edit]

Ohm law


where:

R is resistance (ohms, Ω),
V is voltage (volts, V),
I is current (amperes, A).

Conductance[edit]

Conductance (G) is defined as the inverse of resistance, calculated as:

where:

G is conductance (siemens, S).

Voltage[edit]

Voltage is calculated as:

Current[edit]

Current is calculated as:

Power[edit]

Power is calculated as:

Resistor in AC circuit[edit]

Voltage[edit]

Current[edit]

Power[edit]

Reactance[edit]

Impedance[edit]

Phase[edit]

v and i are in phase

Resistor Configuration[edit]

Resistors in Series[edit]

For n resitors connected adjacent to each other as shown

The total resistance

For 2 series resistor of same value

Resistors in parallel[edit]

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]

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]

Color Significant
figures
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]

External Links[edit]