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Fotolia.com Through Ohm's law, you can calculate the voltage (V), current (I) and resistance (R) of a DC circuit. From that you can also calculate the power at any point in the circuit.

Follow Ohm's law: Voltage (V) = Current (I) times Resistance (R).

Use this example to calculate DC voltage. If I is 0.5 amps-DC (500 milliamps DC or 500 mADC), and R is 100 ohms:

V = I * R = 0.5 * 100 = 50 volts, or 50 VDC

Calculate power if you know both current and voltage:

Power (watts) = Voltage (volts) * Current (amps) P = V * I

Divide DC voltage by 1,000 to express in kilovolts, or KVDC:

17,250 VDC / 1,000 = 17.25 KVDC

Calculate small voltages. It may be more convenient to express the DC voltage in millivolts by multiplying by 1,000:

0.03215 VDC * 1,000 = 32.15 mVDC

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