Uploaded August 2021 | Updated September 2026, 2 weeks ago

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It is quite easy to know how to calculate the resistance of a number of resistors in parallel. As the current is shared between the resistors we find that the reciprocals of the resistance are added together. The formula is one upon Rtotal equals one upon R1 plus one upon R2 plus one upon R3 and so forth.

So if we have resistors of 100 ohms, 50 ohms and 20 ohms in parallel we see that one upon the total resistance is equal to 0.01 + 0.02 plus 0.05 = 0.08, so the resistance is 12.5 ohms

If we only have two resistors in parallel the formula simplifies to this. so if we have resistors of 100 ohms and fifty ohms in parallel, we substitute the values into the equation and discover that the overall resistance is 33.3 ohms.

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