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Electronic 101: Resistor

As we start to introduce electronic component, there is one small components which mostly commonly used in circuit design or wiring. Why do we need Resistor? Does circuit become resistance?

Resistor

  • Resistors are passive electrical components that reduce the flow of electrical current in a circuit.
  • They are one of the most common components and can be found in almost every electrical networks and electronic circuit.
  • Resistance is the property of materials to resist the flow of electricity, and it is governed by Ohm’s Law. The resistance is expressed in ohms.
  • There are many different resistor types and constructions.
Resistor circuit symbols

Resistor Colour Code

  • The reading direction might not always be clear. Sometimes the increased space between band 3 and 4 give away the reading direction. Also, the first band is usually the closest to a lead. A gold or silver band (the tolerance) is always the last band.
  • It is a good practice to check the manufacturer’s documentation to be sure about the used coding system. Even better is to measure the resistance with a multi-meter.
resistor color code chart

Calculating Resistor Values

  • The Resistor Colour Code system is all well and good but we need to understand how to apply it in order to get the correct value of the resistor. The “left-hand” or the most significant coloured band is the band which is nearest to a connecting lead with the colour coded bands being read from left-to-right as follows:
    • Digit, Digit, Multiplier = Colour, Colour x 10 colour  in Ohm’s (Ω)
    • For example, a resistor has the following coloured markings;
    • Yellow Violet Red = 4 7 2 = 4 7 x 102 = 4700Ω or 4k7 Ohm.
  • The fourth and fifth bands are used to determine the percentage tolerance of the resistor.
  • Typical resistor tolerances for film resistors range from 1% to 10% while carbon resistors have tolerances up to 20%. Resistors with tolerances lower than 2% are called precision resistors with the or lower tolerance resistors being more expensive.

Hope you read and understand how to select and use a resistor for circuit. See you again and take good care of your health.

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