Electronics – Resistor

 

RESISTOR

  • Resistor is a passive electronic component.
  • its function is to limit(resist) the flow of current or divide the voltage in a circuit.
  • The unit of the resister is ohm(Ω).
  • The resistance r of any material is proportional to its length and inversely proportional to its area of cross section A.
  • R=ρl/A
  • ρ=specific resistance or resistivity of the material.

 

Resistor Type

  • Fixed Type
  • Variable Type

Fixed Resister

  • wire wound resistor
  • carbon film resistor
  • metal film resistor
  • carbon composition resistor
  • carbon resistor
  • film type resistor
  • chip resistor
  • fusible

 

Variable Resister

  • Rheostat
  • Potentiometer
  • Trimmer
  • Pre set

 

RESISTER APPLICATION

  • variable resister is used in volume control in the TV application,

Examples:

  • find the resistance of a copper wire of 0.75km long and having a cross sectional area of 0.01cm2. (take ρ=1.72×10-8ohm-m).
    • ANS=12.9ohm
  • find the cross sectional area of an aluminium wire of 700m long and having a resistance of 0.24ohm (take ρ=2.83×10-8ohm-m)
    • ANS=8.254×10-5m2.

SMD Resistors Examples

Find out the component value

First two digits are value and last digits are multiplier,

  • 333 –        33000          –        33kΩ
  • 347 –        340000000  –        340kΩ
  • 4421 –        4420           –        4kΩ
  • 44R –        44Ω
  • 4R4 –        4Ω
  • R44 –        44Ω
  • 44K –        44kΩ
  • 4K4 –        4KΩ
  • K44 –        44KΩ
  • 44M –        44MΩ
  • 4M4 –        4MΩ
  • M44 –        44MΩ

Reference website :

  • SMD Resistor Package Code
    • http://www.resistorguide.com/resistor-sizes-and-packages/

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