ESD discharge path

[jamesnguyen]

Hello all,

Would someone please explain why there an ESD discharge to a phone lying on a _wooden_ table?

For what I understand, electrical current only flows when there is a closed electrical path. With the phone lying on a wooden table, how does the ESD (from an ESD gun or from a person) discharge to the phone when there is no common "ground"?

Regards,
James

 

[rbulsara]

The charge does not discharge to the wood, it equalizes between the phone and the new body touching it.

I would think, an ESD gun would provide a path to its grounding conductor. (haven't used one)

Rafiq Bulsara

http://www.srengineersct.com

 

[VEBill]

It's nothing new...

Most metal interior door knobs inside houses are installed onto interior wooden doors that are ighly insulated from "ground". But given the right (wrong?) circumstances, can make your arm numb with a good static shock. Almost exactly the same situation.

The next part of the experiment would be to shuffle your feet to build up a huge static charge on your body, and then have someone toss you a door knob (or mobile phone).

 

[IRstuff]

Not sure why that's surprising. You, yourself, are a, isolated system, so how did the charge get onto you in the first place? You, hopefully, didn't get connected to a 25kV supply, right?

Static electricity is all about relative motion that strips electrons from something, which builds up an electric field on the object that the electrons now reside. ANYTHING that has a lower electric field can, and will, be the object of a discharge. That's why PC boards need to be completely enclosed in an ESD container of some sort at all times. That's why you can get a shock from your shopping cart, which has rubber or plastic wheels. That's why you can get a shock from your car, which has rubber tires.

TTFN

FAQ731-376
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[Warpspeed]

Electrostatic discharge can occur between any two objects, if the potential difference is there.

Neither need be earthed.
This is a transfer of static charge, it does not require a closed circuit for momentary current flow for the charge potentials equalize.

 

[2dye4]

ESD follows a slightly different rule.

A person moving against another material either accumulates an excess or deficit of electrons on their body.

The electrons if excess seek to spread out and any conductive object touched will absorb some of the electrons until a balance occurs.

Very similar with a deficit of electrons. They flow to correct the imbalance.