Request the formula of resistance when making LED light string. And the algorithm of resistance power

Request the formula of resistance when making LED light string. And the algorithm of resistance power

Resistance = (input voltage - led voltage drop * number of LEDs in series) / LED working current
After calculation, the resistance value is the same as the conventional resistance value
Resistance actual power = (input voltage - led voltage drop * number of LEDs in series) ^ 2 / actual resistance value
The rated power of the resistor is more than 2 times of the actual power

The formula of resistance

Definition formula: r = u / I,
The determinant: r = PL / s

Calculation formula of resistance
For example, how to reduce 10V 1a to 5V 0.5A

Use Ohm's law. V / a = ohm. Resistance equals 10 ohm

The voltage, current and resistance of the conductor can be calculated by the charge quantity of the conductor cross section is 50 Coulomb, the time is 30 seconds and the electric work is 120 J

I (current) = q (amount of charge) / T (time)
So the current = 50 / 30 = 1.67a
W (electric work) = P (power) t (time) = u (voltage) I (current) t (time)
So the voltage = 120 / 1.67/30 = 2.4V
I (current) = u (voltage) / R (resistance)
So the resistance = 2.4 / 1.67 = 1.44 Ω