How is it possible to have high voltage with very little current?

[Zanderist]

By this I mean in the extreme case of a taser, and in the not so extreme case limiting the current to digital ICs as to not burn out the chip through excessive current.

What makes me unsure about this is ohm's law, V=IR.

So in one example like the Taser, where it's output is 5,000 volts, and the resistance of air would maybe be around 10^8 ohms. That should mean 5x10^-5 amps.


But when it comes into contact with the human body, which the resistance there drop to be around 300- 1000 ohms. Assuming average resistance to be 650 ohms it should be up around 7.69 amps. However I think what limits this is the current able to be supplied from the 9 volt battery operating a taser.


Some input.

 

[Syncopator]

The high voltage causes the air to ionise, which reduces its resistance.

 

[BradtheRad]

Generally when talking about high voltage on a small scale, the source itself is high impedance.

Hence there isn't much current available. Even if the load is low ohms, it still wont' get much current.

It's not a rule, but it serves to reduce apprehension among the uninformed public.

This includes tasers, static electricity generated when we walk on the rug, automotive spark plug wiring, etc. These are low current.

On the other hand this 'rule' doesn't apply when talking about electric power lines, or lightning... Then the source is low impedance. You touch a wire, you get high current. However the public is not normally in contact with these.