# What causes an electric shock - Current or Voltage?

Though voltage and current are two interdependent physical quantity, I would like to know what gives more "shock" to a person - Voltage or Current? In simple words, will it cause more "electric - shock" when the voltage is high or Current is more?

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– Qmechanic♦ Sep 14 '12 at 20:18

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Lots of very good informed answers in that related question – Jaime Sep 14 '12 at 22:05

## 6 Answers

You'd have to define 'shock', but what kills you is enough current during enough time, not voltage. Of course you need enough voltage to keep the current going over your body's resistance, but it definitely plays a secondary role.

In a former professional life I worked developing Residual Current Circuit Breakers, and 30 mA is the usual rating for devices aiming at protecting lives. In wet environments, such as bathrooms or swimming pools, sometimes 10 mA is recommended.

According to wikipedia's RCCB article, 25-40 ms of 30 mA is enough to send your heart into fibrillation, which probably qualifies as a pretty strong shock. That would require your heart being in the path of the current, though. This link has more information on what to expect depending, again, on the current, not the voltage.

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I suggest this is self evident. You can have a high voltage between two metal plates and put your hand through safely as long as you do not touch them. Otherwise nobody would be able to repair fuses so close to live wires. If there is no current there is no damage, it is the current we feel as "shock". – anna v Sep 15 '12 at 4:22

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@annav, this problem is in the context of a circuit which implies a closed path for a current to exist. While I appreciate the point you've made, I believe it is actually out of context as there is no circuit in your example. – Alfred Centauri Sep 15 '12 at 21:43

You see, current in one direction indicates the flow of free electrons in the other direction. Hence, current flows. But voltage does not flow. It's actually the work done per unit charge. (Joule/Coulomb). In other words, it's an energy or simply the potential difference between two points. Sometimes, a bird does not get a shock while resting on a carrier wire (Not all time the bird sits on the same wire). Whereas By touching the live wire and ground, we create a potential difference (a path which is sufficient enough for current to flow) with live wire relative to earth. Hence, we get a shock...

Electric shock is the sufficient amount of current flowing through human body which the person could feel. But, this doesn't mean that shock is not caused by Voltage. Of course, it depends upon voltage which is given by Ohm's law... $$I=\frac{V}{R}$$

The shock your body feels, depends upon the applied voltage & resistance of your body. If your body has a resistance of about 10,000 $\Omega$, and the voltage is 230 V, then $$I=\frac{230}{10000}=23 mA$$

You would get a shock, but seriously... (You can't let go off this current)

Hence, you cannot differentiate a shock based on voltage or current. It depends on both voltage and resistance of your body (which implies current).

Here's a page which shows current paths and another one which provides comparison info..!

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If we model the path for the current through the human body as a resistor, then by Ohm's law, the current and voltage are proportional.

That is, a greater current through the body will be associated with a greater voltage across the body.

Having said that, let's consider the source of the shock. It is the case that sources may produce a large voltage but are not capable or sourcing significant current. These sources are said to have high internal resistance.

The point is that a high-voltage source with high internal resistance may not give you much of a shock at all while a lower voltage source with low internal resistance may kill you.

So, there really isn't a simple answer to your question other than "it depends".

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The shock is the product of the current and the voltage, so in principle you need both. A friction spark from your shoe is high voltage by low ampage, but a shock from a power main is high ampage and comparatively low voltage.

The type of current, whether it is alternating or steady, is also important, as an alternating current will interfere with biological processes more than a steady current. But the energy deposited is the product of the two, so it is not meaningful to separate them out.

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Thanks for your quick response Ron but I would like to understand two more points on this : 1. When a bird sits on high voltage wire, nothing happens - of course the conductivity is not there so in spite of high voltage there is no "electric-shock".. Doesn't that suggest "Voltage" has no role in the intensity of the "shock" ? – Tabish Sep 14 '12 at 20:17
2. When you say "shock is the product of the current and the voltage", do you say this is how we can quantify the intensity of "shock" ? Is this the actual formula ? – Tabish Sep 14 '12 at 20:24
@Tabish: For the first thing, by voltage, one always means "voltage difference", the bird has no voltage difference between it's feet, so there is no effect. The product is the energy delivered by the shock, so it's how much you heat up, how much burning you get at the skin and flesh, but it isn't the severity of stopping your heart, which is a different thing, related to the electrical flows that regulate the heartbeat. Also, in terms of feeling the shock, setting up nerve impulses is not by power, but by the change in intermembrane voltages, but power is good rough guide to the effect. – Ron Maimon Sep 14 '12 at 20:33
Thanks Qmechanic, It helped. Thanks Ron for taking time to address this. – Tabish Sep 14 '12 at 20:36
"A friction spark from your shoe is high voltage by low ampage"  No, it's several amps.  It's harmless because of the short duration. – endolith May 11 at 4:27
show 3 more comments

Higher voltage causes more shock at the same wattage.

Low-voltage high-current exposure will be felt as warming up not as a shock.

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Could you please site any source to support it? – Tabish Sep 14 '12 at 20:43
low-voltage high-current will actually kill you, so you may not actually feel the shock... – Jaime Sep 14 '12 at 22:02
@Jaime it will fry you. – Anixx Sep 14 '12 at 22:13
How can a low voltage create a high current through a human being with high resistance? – endolith May 11 at 4:28

the current generates the heat.....but the voltage (potential difference) generates shock...so i think shock is generat due to high voltage!!

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## protected by Qmechanic♦Feb 15 at 18:26

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