Resistor types, symbols, parameters

Resistors are passive electronic components with high usage in electronic devices .

Principal characteristic of the resistors is resistance (opposition to current flow ) .Are many types of resistors :  for hard currents , for light currents , fixed value resistors , variable resistors and other types  .This types of resistors presented can be classify  by other parameters and manufactured process in many categories .

Main parameters of resistor are :

-tolerance t is noted in percents and represents the maximum accepted deviation of real resistance over the nominal value Rn  .

- dispersion power and nominal voltage Un represents the maximum electrical power  supported by the resistor .

Nominal standard power rating in watts for resistor are : .05, 0.1, 0.125, 0.25, 0.5., 1, 2, 4, 6,  12, 16, 25, 40, 50, 100W .

Usual the for a long life of the resistor the dispersed power from the circuit must be a ½ than nominal power .

Are many types of resistors and each type can be marked with a special standard symbol  .The main symbols of resistors can be viewed in the table bellow .

a: resistor , general symbol

b: resistor , tolerated symbol

c: resistor , un-standard  symbol

d: resistor with variable resistance

e: resistor with mobile contact

f: resistor with mobile contact and  stop position

g: potentiometer with mobile contact

h: potentiometer with mobile contact, general symbol

i: potentiometer with preset adjustment

j: two plugs resistor

k: shunt resistor

l: thermal resistor

m: thermistor general symbol

n: thermistor tolerated symbol

o: varistor general symbol

p: varistor tolerated symbol

The main parameters of the resistors can be marked using many methods like :

-color code marked on the body of the resistors with colored bands

- with letters

- with alphanumeric codes