Electrical – Does voltage and current have an inverse relationship in DC power transmission

I'm assuming we are talking in terms of DC here to keep things simple.

Voltage is a measure of how much a single electron's energy changes across the circuit. Current is how many electrons are flowing through a circuit. Multiply those two values to get the rate of energy transfer, or power. If all you have is a measure of current, you know how many electrons are flowing through the circuit, but not how much their energy is changing.

You are correct that voltage induces current, and that voltage and current are interrelated. Ohm's law is the simplest case of that. You can derive a circuit's power from current and it's resistance using known formulas. And even more simply, if you know current is flowing you know the circuit is dissipating power, even if you don't know how much (as the other commenters have said)

All LEDs can be modelled as zener diodes with a colour/substrate specific forward voltage Vf and a series resistive Rs, where they combine both to give the Vf at rated current. Rs tends to be small so you can neglect it for approximations of adding current limiting series resistors. (see below)

Therefore the current is non-linear and proportional to the voltage difference between the supply and the Vf drop at desired current.

Batteries with low voltage variation are ideal such as Lithium primary cells. Most White flashlights using 3V per LED use these without series resistors as the Li cell is also 3V. However they may be specify a sorted bin of LED's to achieve this.

My Rule of Thumb is to string arrays of LED's such that the voltage difference is ~1V for the current limiting Resistor for a fixed regulator. If the supply range has a wide range, e.g. 10 ~15V then a constant current sink circuit is best.

Additional Info

For more accuracy over a wider range of currents, you can determine the Rs value from the specsheets for a given temperature. The Vf forward voltage also is a function of temperature which affects the results slightly. THe Rs of LED's is much lower than the dynamic Rs of Zeners using silicon junctions.

• 20mA HB devices are <20 ohms.
• 300mA HB devices are < 2 ohms.
• 1Amp power modules are ~ 0.3 ohm.
• Rs for LED arrays , add in series, and divide in parallel.
• Old technology LEDs were much higher Rs values.
• Rs will reduce as the current increases but you can approximate it at the 10% of rated current value and extrapolate if the device stays at constant temp.
• Because of the Shockley effect with voltage variationmyou can actually calculate the junction temperature from the voltage drop of a calibrated LED.