How to Calculate DC Currents
- 1). Determine the voltage and resistance of the circuit. Calculation of current is basic electronics theory. These two variables must be determined before current can be calculated.
- 2). Convert all variables to the proper unit designations. Volts and Ohms must be converted to like units. Most DC circuits use small voltages; a car electrical system is 12 volts. Resistors, however, can range from single digits to mega-ohms (millions of ohms). A 1K resistor would be 1000 ohms. This is the number to use in the calculation of current.
- 3). Calculate current (amps) by dividing volts by resistance. Ohm's Law states any element of a DC electrical circuit can be determined, so long as the other two variables are known.
- 4). Expect the amperage to be small in a DC circuit. For instance, a 9-volt input across 1K of resistance pulls .009 amps (9 milliamps) of current.
- 5). Check your answer. Multiply the calculated amps by the measured volts. The answer should be the known resistance of the circuit.
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