Power and Voltage Help (I blanked)!

Thread Starter


Joined Jan 1, 2016
Hey everyone, I'm having a 'blanking' moment:
Today, my teacher gave us an example of an electrical source that had enough power to power a LED light, but not enough voltage. We then had to offer a suggestion to change the circuit in order to make enough voltage.
Can someone please explain how you can have enough power, but not enough voltage? I don't see how this fits in the general power-voltage relationship.

Thank you in advance!


Joined Apr 11, 2010
Power is what? In other words, power is the relationship between what two values!

The answer is P=VxI. If the voltage is too low, and the current available is higher than necessary - you have sufficient power but not enough voltage.

Take a typical but mythical LED circuit for illustration. The LED specs say it has a forward voltage of 2V and typical current of 15ma. It's power requirement would be 0.03W

Now consider a power supply of 1V and 30ma. Power is also 0.03W. But there is insufficient voltage to illuminate the LED; it requires 2V.