Resistor component

Resistors are the most common component in electronics. The better you understand them, the easier learning everything else in electronics will be.

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Basic electrical properties

  • Limits current to series components, from power supply, etc.
  • Divides voltage
  • Generates heat (power)
1K and 10K resistor color code stripes diagram for 1000 and 10000 ohm by Electronzap Electronzapdotcom
1K and 10K resistor color code stripes diagram for 1000 and 10000 ohm by Electronzap Electronzapdotcom

Resistors have resistance. That means that they limit current based on the voltage across them.

  • Ohms: (Ω symbol) – The unit used to indicate the amount of resistance.

Resistors also get hot due to current being forced through them.

  • Wattage rating/Power (P): The ability of a resistor (or other component) to dissipate heat. Most resistors are 1/4W (one quarter watt). Wattage should actually be kept 1/2 of the rated value, so 1/8W (0.125W) or less for a 1/4W (0.25W) rated resistor. Multiply the voltage across the resistor by the current flowing through it to find the watts …. P = V/I

Diagram

The primary role of the resistor component is to limit current. Here is one way to build a circuit on a breadboard where a resistor limits current going through an LED.

9V battery with snap wires to power current limiting resistor with LED circuit on breadbard diagram by electronzap electronzapdotcom
9V battery with snap wires to power current limiting resistor with LED circuit on breadbard diagram by electronzap electronzapdotcom

More detailed resistor information

Terminology and other general properties.

Resistor component 1K blue through hole schematics unit symbol diagram by electronzap electronzapdotcom
Resistor component 1K blue through hole schematics unit symbol diagram by electronzap electronzapdotcom

  • Through hole resistors, which hobbyists mostly use, are usually blue (sometimes beige), with 5 stripes/bands (4 for beige) that indicate it’s rated value and tolerance.
  • Ohms: The unit of resistance. Higher value resistors result in less current for a given voltage.
  • Tolerance: Percentage higher or lower than the rated value that can be expected. Typically 1% for blue resistors and 5% for beige resistors.
  • Ω (Greek letter Omega) is the symbol used to indicated resistance in ohms. 1KΩ is one thousand ohms (one kilohms). Also commonly just referred to as a 1K resistor.
  • Schematic symbol is almost always a jagged line when drawn by someone in the US, while it is often drawn as a rectangle elsewhere. The recommended value is usually written  next to it (in the rectangle). It’s usually safe to assume that a 1/4W resistor will be work unless a different wattage is noted.
  • From time to time, you will see a resistor value written like 1K5. That indicates that it is a 1,500Ω (1.5K) resistor. The K for Kilo is sometimes used to replace the decimal point because it is easy to not see the decimal point.
Recommended video

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Electronics course 1 Resistor component limiting current Ohms law and multimeter measurements

Main resistor topics

Other basic components

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