# Why exactly do we feel a shock when we place our hand into a conducting solution?

I have a very naive question.

Suppose you have pure water in a flask, and you place two ends of a copper wire (which are connected to a battery) into the water.

If you were to place your hand into the water, you would not feel any shock, as pure water does not conduct electricity.

However, if you add an electrolyte like common salt to the same water, you would probably feel a shock.

Adding salt makes the solution conducting. When the two wires are placed in the solution, the ions are attracted to the end of the wire which has an opposite charge.

However, what does the movement of those ions have to do with whether or not your hand feels a shock? Shouldn't whether you feel a shock just depend on what resistance your hand offers?

when you immerse your hand into the conducting water, your skin is connected to the conducting medium. The charge being transported through the water is then faced with a choice, as follows.

Your hand and the water surrounding it represent two resistors in parallel. If your hand is more conductive than the water, the electricity will flow preferentially through your hand and you will feel a shock.

If the water is more conductive than your hand, most of the charge transport will occur through the water, and not much will occur in your hand- and you will feel little or no shock.

Dry skin is an insulator, but it readily absorbs water and becomes a good conductor because of the salt it contains. This means you might not immediately feel a shock when you splunge your hand into the water, but you will as the outer layers of your skin get hydrated.

Whether you feel a shock depends on how much current flows through your hand. How much current flows through your hand depends on the resistance along the whole path of the circuit, not just in your hand.

For example, if you put a battery on a table and then put a resistor a few inches away from the battery, there would be no current flowing through the resistor, because air is a very bad conductor. But if you now connect that same resistor, with the same resistance, to the battery using wires, now there is current flowing through the resistor, because the resistance along the rest of the path has decreased tremendously. This is despite the fact that the resistance of the resistor didn't change.

• And as niels nielsen pointed out, if there is a low-resistance path that doesn't involve your hand, the current through your hand will be lower than if there wasn't. Commented Jun 9, 2020 at 22:49

If I may ask, why do you feel a twinge when you step on a nail or a pin pricks you? The same way your nerves make you feel the painful sensation of stepping on a nail is the same way that they react when current flows through your hand. It's not that current flows through your body but how your nervous system reacts to the current flow. When your hand goes across a salt solution connected to a battery, electrons zip through the solution unto your hands and your body makes you react to it by giving you the sensation of a shock.

• @PM2Ring I mean "to step" on a nail Commented Jun 10, 2020 at 10:27

you will be shocked to hear this that your hand becomes a resistance R, when you touch the liquid, small amount of electric current pass through your body, and the moment of ions make you feel the current or shock here. these ions are the current carriers, and when you placed your hand in non-ionizable you haven't felt the shock because there was no one to carry current through your body, the ** intensity of shock** depend upon the battery, not on your hand.because of the battery more the power of battery more the potential difference between you and the liquid solution and more the current you feel. our body is among the bad resistant species to the current, maybe because of iron in our blood. here the potential is not constant so we will have to look at the graph between potential $$V$$ and $$x$$. like this ,and your and this will create a circuit like this .so there will be some voltage ΔV across your hand when you put it in the liquid. So it's like the resistor network shown in the second image. Effectively your hand is a resitor with a voltage ΔV across it, so a current flows through your hand I = ΔV/R.

If the voltage is big enough the current will get large enough to give you a shock.that's what I said in my above comments .(note; images are created by @johnrennie, and with his permission, I used them here)..

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