Sometimes in electronics you have no alternative but to whip out your calculator and do a little math. The most likely reason for doing this is to calculate how much resistance you need for a given situation, how much current a circuit will pull, or how much voltage will be dropped between two points in a circuit. All of these calculations can be made by using one of the following formulas derived from Ohm’s Law:

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In the above formulas, V represents voltage (in volts, naturally), I represents current (in amperes), and R represents resistance in ohms.