Electrostatic discharge current

[Nicolas_1994]

I understand that electrically charged objects such as a rubber balloon or even the human body can hold several thousands of volts.

What's troubling me is that I know the current that results from an electrostatic discharge is not enough to cause serious damage or kill a human, yet if you touch a high power low voltage DC source you can get a painful shock or even die.

I know that the human body is complicated to model, but I imagine that, provided the current only flows through the skin (little change in resistivity), we could approximate it to a resistor of very high value (several kOhms).

That being said, the only explanation that I can come up with is that a charged object acts as a capacitor with very little capacitance, which allow it to discharge very quickly, leading to a very short pulse of a realtively high peak current (total power dissipation being very low). On the other hand the DC source can provide a steady current that shoud be enough to hurt.

In short, an ESD only provides current for a very short period of time, not resulting in any damage, while DC sources can maintain the current, resulting in greater damages.

Please, if any of you could shed some light into this matter, I'd be very greatful.

 

[davenn]

Hi There
welcome to PF

yet if you touch a high power low voltage DC source you can get a painful shock or even die.

what is your definition of that ?

12V car battery that can deliver 900A won't hurt me if I touch the terminals

I know that the human body is complicated to model, but I imagine that, provided the current only flows through the skin (little change in resistivity), we could approximate it to a resistor of very high value (several kOhms).

dry skin resistance is in the Meg Ohms range

That being said, the only explanation that I can come up with is that a charged object acts as a capacitor with very little capacitance, which allow it to discharge very quickly, leading to a very short pulse of a realtively high peak current (total power dissipation being very low). On the other hand the DC source can provide a steady current that shoud be enough to hurt.

no, instead consider the other option that the several 1000's of volts is enough to overcome the skin resistance and allow a small current (VERY SMALL) to flow

In short, an ESD only provides current for a very short period of time, not resulting in any damage, while DC sources can maintain the current, resulting in greater damages.

sorta, sort of not

consider a lightning discharge VERY brief, very large voltages and currents, and can do horrific amounts of damage

Dave