# Why does current from a grounded electrical outlet flow through me if I stay on the floor made out of a dielectric material?

Why does current from a grounded electrical outlet flow through me when I touch a "hot" terminal, if stay on the floor made of a dielectric material?

Consider an AC voltage source, such as a wall socket, at $220 \, \mathrm{V}$ and $60 \, \mathrm{Hz}.$ I stay on the wood, tile, or another dielectric material, which the floor commonly consists. The floor is dry. I touch only one terminal (not ground), it hurts me. How?

I know for sure, that the screwdriver-indicator works because of resistor with huge resistance, like $2000 \, \Omega$ + body resistance, we get $$I ~=~ \frac{220 \, \mathrm{V}}{\sim 3000 \, \Omega} ~=~70 \, \mathrm{mA} \,,$$the current flows, bulb lights, we do not die. Hence the resistance of wood is less than $2 \, \mathrm{k} \Omega \, ?$

• As the mains supply is alternating current the charging and discharging of the capacitance of your body relative to free space (actually your other closer surroundings) causes a small AC current to flow and will illuminate the test indicator. You are feeling this real current because if flows into you from a single point. – KalleMP Sep 8 '18 at 20:00

As the mains supply is alternating current the charging and discharging of the capacitance of your body relative to free space (actually your other closer surroundings) causes a small AC current to flow and will illuminate the test indicator.

You are feeling this real current because if flows into you from a single point.

Also even a poor conductor like rubber and wood will still conduct a bit.

• Poor dielectric You meant? – user205695 Sep 8 '18 at 20:04
• @Artur Nope, they are reasonable dielectrics but poor conductors. – KalleMP Sep 8 '18 at 20:05
• Translated poor wrong, never mind – user205695 Sep 8 '18 at 20:07
• So, basically the answer is body capacitance. I asked this physics.stackexchange.com/q/427519/205695 question, so You mean, if I'll be in the jump the current will flow through me, anyway? Or the fact that I'm staying on the wood, that actually is a better conductor, then the air, and will let some 0.000 current flow plays a big role due to a huge capacitance of a human body? – user205695 Sep 8 '18 at 20:13
• If you are brave you can experiment. Take 3 drinking glasses and place on floor, place strong wood board (upside down small table) on glasses and stand on board. Redo your test, if shock is less then wood is not good enough insulator and glass is better, if shock is the same then you are good capacitor and wood and glass are both good insulators. – KalleMP Sep 8 '18 at 20:25

Just wanted to clarify a couple of points.

First, even if the floor is covered by tile (good dielectric), you don't always know what is underneath it: it could be damp plywood or a pipe, which would be capacitively coupled to your body, despite the tile in-between. The current level still won't be significant, but it could be higher than expected.

Second, the effective resistance of a screwdriver-indicator should be much greater than $2000ohm$: $70mA$ current could be lethal. Below is a table copied from this OSHA site, which shows the effect of human body exposure to various current levels for $1$ second: