Static Shock Question

Thread Starter

chilli42

Joined Jan 5, 2024
3
Hi,

Please be kind - have probably a silly question about static electricit, the type when you walk across a carpet and touch something and you get a spark/shock on your finger.

Hoping someone here can answer as I’m getting confused.

If I’m holding say a cell phone in a rubber case and I have built up static charge on me, could I experience that spark/shock if a finger touched an exposed metal button on the phone (not covered by the case), or because I’m already holding the phone, would that not happen. Would I only get the shock if I were to touch something separate, like a door handle?

Hope that make sense.
 

MrChips

Joined Oct 2, 2009
30,974
Hi,

Please be kind - have probably a silly question about static electricit, the type when you walk across a carpet and touch something and you get a spark/shock on your finger.

Hoping someone here can answer as I’m getting confused.

If I’m holding say a cell phone in a rubber case and I have built up static charge on me, could I experience that spark/shock if a finger touched an exposed metal button on the phone (not covered by the case), or because I’m already holding the phone, would that not happen. Would I only get the shock if I were to touch something separate, like a door handle?

Hope that make sense.
You get a spark/shock when you touch something that attempts to neutralize the charge you have accumulated on your body.

A door handle is more than just the handle. It is also a part of the door which, believe it or not, also conducts away the accumulated charge.

The cell phone is not large enough hence you will not feel anything.
 

Thread Starter

chilli42

Joined Jan 5, 2024
3
You get a spark/shock when you touch something that attempts to neutralize the charge you have accumulated on your body.

A door handle is more than just the handle. It is also a part of the door which, believe it or not, also conducts away the accumulated charge.

The cell phone is not large enough hence you will not feel anything.
thx. But is charge still going through the phone and not big enough so you don’t feel it, or no charge at all is discharged because it’s not big enough?
 

MisterBill2

Joined Jan 23, 2018
19,008
NO, touching a metal part of the phone that you have been holding while you built up the static charge will not deliver a static shock, neither felt nor too small to be felt. That is because the charge you were building up also charges the whole body of the phone by means of surface leakage. The exception would be if the phone was connected to a plug-in charger while you were holding it. then the answer would be " probably not, but maybe. BUT more likely that would prevent building up much of a static charge.
 

Tonyr1084

Joined Sep 24, 2015
7,957
If I’m holding say a cell phone in a rubber case and I have built up static charge on me, could I experience that spark/shock if a finger touched an exposed metal button on the phone (not covered by the case), or because I’m already holding the phone, would that not happen. Would I only get the shock if I were to touch something separate, like a door handle?
Holding my comment for the end of this post.
The cell phone is not large enough hence you will not feel anything.
Disagree. Hold for final comment please
is charge still going through the phone and not big enough so you don’t feel it
Static charges as LOW as 3KVS (Kilo Volts Static) are nearly imperceivable to the human touch. I know, I used to set up a demonstration plate that was charged to 3KVS and have students touch it. Many students were too afraid to touch it but the bold ones to the last said they couldn't feel a thing. However, when barely touching the plate yes, you could feel a tremendously slight discharge. A 3KVS discharge is way more than enough to destroy MOST electronics if not protected by some sort of surge protection.
NO, touching a metal part of the phone that you have been holding while you built up the static charge will not deliver a static shock, neither felt nor too small to be felt.
This is my end comment. Yes, this is absolutely the truth. The phone in your hand is going to be at the same potential as your body. Touching something that is at the same state of charge will experience no electron movement.

Mentioned 3KVS because that's just about the threshold that you can begin to feel the discharge. The human body can store up to and above 50KVS. Those are the cold dry mornings when you get out of your car to fill the gas tank. The first thing you do is touch the metal filler cover to open it. BANG! You discharged. Then you grab the nozzle. Soon as you touched it you equalized whatever remaining charge you may have built up. Now you, the nozzle and the car are all at the same basic state of charge. But it's cold outside. You sit in the car while the tank fills. You grab the plastic non-conductive door handle, push the door open via the door panel which is also not conductive, get out of the car, and as you slide off the seat you generate as much as 50KVS state of charge on your body and clothing, cell phone included, you reach for the nozzle in an atmosphere that is rich in gas vapors. As you touch the nozzle you discharge and the spark starts a fire. This occurs more often for women because of two things; they tend to sit in the car while the tank fills, and they wear synthetic fabrics such as nylon, rayon and other stuff that is high on the triboelectric scale. Look that up if you like.

IF you get out of the car, before reaching for the nozzle, put your hand on the surface of the car. Even though it's a painted surface you'll still discharge most of the static charge. THEN take the nozzle out of the filler neck.

Bottom line for your question: Will the cell phone be damaged? No. Because it's at the same potential as you. Whether it's in your hand or in your pocket, the static field charges everything in close contact.
 

Tonyr1084

Joined Sep 24, 2015
7,957
touching a metal part of the phone that you have been holding while you built up the static charge will not deliver a static shock, neither felt nor too small to be felt
The ONLY way you might damage your phone is if you use the phone to touch something grounded or at a substantially lower state of charge. Whatever static charge you've stored up will discharge THROUGH the phone but only if the phone is the first thing to touch something grounded. You wouldn't touch the doorknob with your phone first, so it's not likely you'll damage your phone by touching it.

@MisterBill2's comment is worth repeating. It's spot on.
 

MrAl

Joined Jun 17, 2014
11,572
Hi,

Please be kind - have probably a silly question about static electricit, the type when you walk across a carpet and touch something and you get a spark/shock on your finger.

Hoping someone here can answer as I’m getting confused.

If I’m holding say a cell phone in a rubber case and I have built up static charge on me, could I experience that spark/shock if a finger touched an exposed metal button on the phone (not covered by the case), or because I’m already holding the phone, would that not happen. Would I only get the shock if I were to touch something separate, like a door handle?

Hope that make sense.
Hi,

This is a little complicated. Let's say in all these cases your body is charged.

1. If your cell phone was floating in mid air when you became charged and you touched the phone, some of the charge would transfer to the phone.
2. If you were holding the phone and you touched it, there should be no charge movement.

The reason there is some transfer of charge in case #1 above was because the phone was insulated from your body due to the distance you are away from the phone. If you got very close to the phone this may change things.
Now that insulation is the key. If the phone is insulated when you alone became charged, then when you touch the phone some charge transfers to the phone. This means if the phone is in a rubber case when you became charged, the transfer (or not) of charge depends on how well the phone was insulated. It's hard to insulate against this kind of thing though so you'd have to have a really good insulator which is not that likely.

Whether or not the phone becomes damaged when there is a transfer of charge depends on how the phone was constructed and how much charge actually transferred to the phone. It's very difficult to predict this because of the variables. It could even be that one model phone blows out while another model survives.

This is something to think about though I guess, interesting that you thought of it. It must be a rare event though because people are separated from their phones a LOT and I have not heard of any phone blowing out randomly when touched. I think that most of the phones do not have metal buttons though.
 

MisterBill2

Joined Jan 23, 2018
19,008
I had an interesting static electricity challenge a few years back with a band at a church. They played standing on a wooden platform covered with nylon carpet. A couple of the band members kept getting big shocks off of the microphones. So I kept getting demands to "fix the leakage from the power feed that was giving them such horrible shocks." Finally I ran a heavy copper cable wrapped around each mic stand, and connected to a copper pipe using an automotive jumper cable clamped to the mic stand and the pipe. The shocks got much worse and I got blamed for that. I suggested doing one practice in stocking feet to see if that helped, They refused. Two weeks later one band member did it, practicing by himself. No shocks! The band leader never did believe me, though. Eventually a spray can of anti-static spry solved the problem.
 
Last edited:
Top