@▷ Resistor Color Code, Tutorial, Formulas, Georg Simon Ohm history, What is "Rho". | Diagram for Schematic

Resistor Color Code, Tutorial, Formulas, Georg Simon Ohm history, What is "Rho".


If you are interested in learning the code by memory, try the steps below to help you 'Learn the Color-code'.
Make sure you add the number to the color, like: 0 is black, 1 is brown, 2 is red, etc. etc.
Do not proceed to step 3 until you know the color-code backwards, forwards, and inside-and-out (trust me!)

Can you 'create' your own resistors? Sure thing, and not difficult. Here is how to do it: Draw a line on a piece of paper with a soft pencil, HB or 2HB will do fine. Make the line thick and about 2 inches (5cm) long. With your multimeter, measure the ohm's value of this line by putting a probe on each side of the line, make sure the probes are touching the carbon from the pencil. The value would probably be around the 800K to 1.5M depending on your thickness of the line and what type of pencil lead is used. If you double the line the resistance will drop considerably, if you erase some of it (length-wise obviously!) the resistance will increase. You can also use carbon with silicon glue and when it dries measure the resistance, or gypsum with carbon mixed, etc. The reason for mentioning these homebrew resistors is that this method was used in World War II to fix equipment when no spare parts were available. My father, who was with the Dutch resistance during WWII, at that time made repairs like this on many occasion.

Main, basic color codes  Step 1: Learn the colors

1.2 ohm The color 'Gold' is not featured in the above table. If the 3rd band is gold it means multiplying by 0.1. Example, 1.2 ohm @ 5% would be brown-red-gold-gold. 12 multiplied by 0.1 gives 1.2 Don't get confused by gold as a resistance or a tolerance value. Just watch the location/posistion of the band.

Tolerance color codes  Step 2: Learn the tolerances.


Step 3: Do the exercises below. (Cheating gets you nowhere :-))
colors Colors I used for 'Gold, Orange, Gray, and Silver'
example1
 1st band, denominator: Brown (1)
 2nd band, denominator: Black (0)
 3rd band, how many zeros (1)
 4th band, tolerance in %: gold (5)
 Answer:  1 0 1 = 100 ohm, 5% tolerance
example2
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example3
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example4
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example5
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________

example6
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example7
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example8
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example9
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example10
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example11
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example12
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example13
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example14
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example15
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________

example16
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example17
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example18
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example19
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example20
 1st band: _____
 2nd band: _____
 3rd band: _____
 4th band, tolerance in %: _____
 Answer: ___________________
example21
 1st band: brown (1)
 2nd band: black (0)
 3rd band: gold  (0.1)
 4th band, tol. in %: red (1-0-0.1 = 1 ohm, 2%)

example22
 1st band: 
 2nd band: 
 3rd band: 
 4th band, tolerance in %: 
 Answer: ___________________
example23
 1st band: 
 2nd band: 
 3rd band: 
 4th band, tolerance in %: 
 Answer: ___________________
example24
 1st band: brown  (1)
 2nd band: white  (9)
 3rd band: yellow (4)
 4th band: brown  (0)
 5th band, tol.in %: brown (1940 ohm = 1.94K, Precision type.)
example25
 1st band: 
 2nd band: 
 3rd band: 
 4th band: 
 5th band, tolerance in %: 
 Answer: ___________________

To get familiarized with abreviations in values, I used below 4700 or 4K7, 1000 or 1K, which is all the same. Every thousand (1000) is called a 'K' which stands for 'Kilo'. The 'M' stands for 'Mega' (million). 1 Mega is 1000K or 1000 000 ohms. So 4K7 means 4 thousand and 7 hundred or 4700 ohms. 6K8 means 6 thousand and 8 hundred or 6800 ohm. One more example, 1M2 means 1million and 200.000 or 1.200000 ohms. Here are a couple more: 1K92=1.92K=1920 ohms, 100E=100 ohms, 19K3=19.3K=19300 ohms, 1M8=1.8M, etc., etc. These abreviations you find everywhere in the industry, schematics, diagrams and whatever. It is normal and takes a bit of time to get used to.
 4700 ohm, 5% = yellow violet red, gold         100 ohm, 2% = brown black brown, red

 1000 ohm, 5% = brown black red, gold            22 ohm, 1% = red red black, brown

  150 ohm, 5% = ________________________        270 ohm, 5% = ________________________

 3300 ohm, 5% = ________________________         10 ohm, 1% = ________________________

  470 ohm, 2% = ________________________      6800 ohm, 10% = ________________________

      3K3, 5% = ________________________             1K, 5% = ________________________

  150 ohm, 1% = ________________________           2M9, 10% = ________________________

     10M, 10% = ________________________     1 Mega Ohm, 5% = ________________________

    1 ohm, 1% = ________________________           3M9, 20% = ________________________

 1200 ohm, 5% = ________________________            1K2, 5% = ________________________

  220 ohm, 1% = ________________________       3300 ohm, 2% = ________________________

   47 ohm, 5% = ________________________        390 ohm, 5% = ________________________

 3900 ohm, 2% = ________________________    100.000 ohm, 5% = ________________________

      10K, 5% = ________________________     10.000 ohm, 5% = ________________________

 1500 ohm, 2% = ________________________            56K, 5% = ________________________

      1M, 10% = ________________________           470K, 1% = ________________________

  1.8 ohm, 2% = ________________________        2.2 ohm, 1% = ________________________

     2K76, 1% = ________________________          94.1K, 2% = ________________________
This should get you started. If it looks difficult to you, don't worry. It is easy. Whenever you have a spare moment practise the color code in your head. It's like learning to ride a bicycle, once you know how to do it you never forget. I, and many others who learned electronics in the 60's and up to the 80's, were taught a little sentence to remember the sequence of the resistor colors like Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, and White, which refers to: "Bad Beer Rips Our Young Guts But Vodka Gives Well". As you will agree this saying no longer applies to the society we live in today for obvious offending reasons. And I'm hessitant to even mention it but fact is, it was part of our 'learning' for decades and so I decided to mention it for reference purposes only.
Good luck my friends!

Just in case, here are the >>> Answers <<< to all the questions above.
Resistor Formulas



Ohm's Law Ohm's Law. R is Resistance, V is Volt, I is Current.

Rho
What exactly is rho you ask? Ohm's Law is not a fundamental law like Newton's Laws or the laws of thermodynamics, but an empirical description of a property shared by many electrical materials. This property of electrical materials is called conductivity. The inverse of that is called resistivity, which where 'Rho' comes in. Just in case you are a bit rusty with your basic math, inverse means that the mathematical relation between the two items, say A and B is: A = 1/B

This is also called the reciprocal. B is the reciprocal of A, so that A*B = 1.

The relationship between conductivity and resistivity is: conductivity = 1/resistivity

Resistivity, represented by the greek letter Rho, (see above), is related to resistance, one of the items in the equation of Ohm's law. Resistance is not just found in resistors, but also in conductors. Wires are conductors. We try to make wires with as little resistance as possible, that is, with as much conductivity as possible. This can be done by decreasing the length of the wire and by increasing the diameter of the wire, and by choosing a material with as much conductivity as possible. These variables, L (length of conductor), A(cross sectional area of conductor) and (symbol for the conductivity of the material) together spell the resistance of the conductor. That is: R = L/( A)
In plain English words, resistance, R, is the ratio of the length (L) of the conductor wire divided by the constant conductivity (the greek sigma ) and by the cross sectional area (A). This formula is used to calculate how much resistance will be present in a wire conductor. You will find that it is important to reduce the resistance in the conductors in circuits. This is because resistance generates heat, and, for many circuits, heat is not desireable. So this formula shows us that one way to do this is to keep the length of conductors to a minimum. That also saves money. Reducing the length of conductors in a circuit will reduce the heat radiated which will keep nearby electronics components from overheating [thus helping them to last longer] and reduce power requirements [== save a little money over time]. Wow! All that information is derived from that one little formula. Formulas are powerful tools.
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