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CSR - Carbon composition resistors.

P1 :About tolerance resistors , what I have understood is that if a 220 Ω resistor has a color band of silver. Then , it’s tolerance = ± 22%. So , resistance of the CSR or the obstruction to the flow of electrons will be in the range of 242 or 198 Ω . Any one number value in this range. From the values 198 to 248 ohm. What does this mean ? Like resistance is obstruction to the flow of electrons. Formula is $R= $$\frac{V}{I}$. Now , the value of V and I should be such that resistance value is always between 198-242 ohm ? It cannot exceed or be lower than this range limit values.

Example in my textbook: enter image description here P2: Also , in a CSR. Is it specified that from which direction the flow of electron is going to start. Left or right. Since online it says that resistors are blind to polarity.

I would like to confirm if for $1st$ part , my understanding is correct or not ?

For $2nd$ part , I am not getting what is the reason and the right answer.

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  • $\begingroup$ what exactly is your question? these are just statements. if you have two questions please post them in two separate posts. $\endgroup$ Jul 26 at 14:19
  • $\begingroup$ Ok. I want to confirm if my meaning or what I have understood is correct or not. $\endgroup$
    – S.M.T
    Jul 26 at 14:19
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For question 1:

The silver band stands for a tolerance of ± 10% this equals a range from 90% to 110%. you just added/subtracted the absolute value of 22Ω but wrote 22%, this is wrong. It should be 90% * 220Ω = 198Ω for the lover limit and 110% * 220Ω = 242Ω. Or ±10% * 220Ω = ±22Ω and then doing 220Ω ± 22Ω.

For question 2

The polarity of carbon composition resistors does not matter. You may have misunderstood something here. The direction from which you read the coloured rings does matter, this may have been the real meaning.

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  • $\begingroup$ Ok. For part 2 , then. From which should I start the electricity. Is there a specific end from which it will start ? $\endgroup$
    – S.M.T
    Jul 26 at 14:26
  • $\begingroup$ Check my edit for your part 1 answer. My textbook has different kind of answer $\endgroup$
    – S.M.T
    Jul 26 at 14:27
  • $\begingroup$ what do you mean by "start the electricity"? the direction of electron flow is irrelevant to this type of component $\endgroup$ Jul 26 at 14:27
  • $\begingroup$ Ok. If it doesn’t matter from which side. Then , we have 3 color bands on the left side and 1 on the right side I.e tolerance band. It does not matter from which side the electrons should flow right. ? $\endgroup$
    – S.M.T
    Jul 26 at 14:28
  • $\begingroup$ yes this type of component can be used in both directions with the same effect. You wrote "± 22%" in your original question but it should have been "±22Ω". $\endgroup$ Jul 26 at 14:32
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From the values 198 to 242 ohm. What does this mean?

If you measure the resistance of the resistor, it should measure a specific value in this range at room temperature, if it is within tolerance. This value can change as the resistor warms up. The value is determined by the manufacturing process.

A batch of resistors would have values falling around the color coded value and tolerance, with few measurements at the extremes. Values should follow a bell curve type of normal distribution. Center will be around 220Ω and no binning for tolerance (not cost effective to test for tolerance on mass produced components).

Actual value will depend on ambient temperature of circuit, aging (value drifts over life - PPM/year), humidity and use and abuse over life cycle.

Is it specified that from which direction the flow of electron is going to start. Left or right.

Resistors have no inherent polarity, but depend upon direction of current going through them and if you are using Conventional Current or Electron Flow (which may be a part of your confusion).

[Conventional Current] Current goes into positive side of resistor. [Electron Flow] Current goes into negative side of resistor.

Now, the value of V and I should be such that resistance value is always between 198-242 ohm? It cannot exceed or be lower than this range limit values.

A damaged resistor can be outside the range. It doesn't mean the circuit will not work or fail, just that the resistor is outside tolerance.

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