Can we light a light bulb with earth's electric field? This is a dumb question. I recently found out that earth has an electric field around 150V/m near it's surface. So,I was wondering if we held the two terminals of the bulb few centimetres apart, verticaly above the ground ,shouldn't the bulb shine? I know this doesn't happen but, I am unable to comprehend this phenomenon. Why can't the earth's electric field generate a potential difference between bulb's terminals?
 A: Local atmospheric current densities are very weak, about $10^{-12}~\text {A}/\text{m}^2$, so per electric power law :
$$ P = VI ,$$
few centimeters apart between two terminals of bulb, would generate only about $\approx 10^{-12}~\text{W}$ of electric power, which clearly is not enough to light-up bulb with nominal $100~\text{W}$ power. Thus, unless bulb somewhat near lightning zone,- it will never happen.
A: A light bulb pops into existence with one of its terminals in the air 1m above the ground and the other terminal in the air 1.05m above the ground, so that there is a potential difference of ~5V across the terminals. What happens right away? A very small amount of charge passes through the light bulb from one terminal to the other (and maybe lights it slightly for a microsecond). Now the voltage across the terminals is 0V. The air immediately next to one terminal is at the same potential as the air immediately next to the other terminal.
What happens after that? Pretty much nothing, because air is basically an insulator. Nothing is going to come along and push more current through the bulb.
The processes that ionize the atmosphere, creating that natural electric field, produce a very, very small current. It's only because air is a very poor conductor that that tiny current is able to build up a significant voltage. As soon as you introduce something that's a better conductor than air, that tiny current develops a tiny voltage, and an even tinier power.
