Back to Basics: Checking Resistors in Series and Parallel




Checking the total value of resistors connected in series is rather simple. You just have to add the total values of each resistor and you get the final value. But it is not that simple when you connect resistors in parallel. You have to take the inverse value of each resistor, sum them up and finally get the inverse of the sum to get the final value of resistors connected in parallel.


To simplify things in the demo, we will take three 10K resistors. 10K resistor has a brown band in the beginning representing a colour code of one, followed by a black band representing zero and then an orange band representing the multiplier of 1000 or 10 to the power of 3. So the value will be 10 x 1000 = 10,000 or 10 Kilo Ohms.

Single 10K resistor on breadboard measures 9.82K, with golden tolerance band of 5%. Selector at 20K position.

Three 10K resistors on breadboard measures 29.6K, with golden tolerance band of 5%. Selector at 200K position.

Two 10K resistors in parallel on breadboard measures 4.91K (About Half), with golden tolerance band of 5%. Selector at 20K position.

Three 10K resistors on breadboard in parallel measures 3.28K (About One Third), with golden tolerance band of 5%. Selector at 20K position. Same value of resistors were used for simplifying the calculations so that it is easy to check by mental calculation. If different values are used, it will be more difficult to calculate like that.


 

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