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Technical support

R = U / I

U = R x I

I = U / R

P = U x I

With R = Restistance (Ω)

        I = Ampere (A)

        U = Volts (V)

        P = Watts (W)


Formula applied in series and used to calculate which resistor is needed to power a 3mm red LED using a 9V battery

P = 20mA x (2v + 2v) = 80 mW

When we put several components in series they will be subjected to the same current, however their voltages are added up. 

Same formula applied to the same two LEDs but this time mounted in parallel

P = (20mA + 20mA) x 2v = 80mW

In a parallel circuit the voltage of the components are equal but their currents are added up