Post History

77%

+5 −0

Q&A Why is the resistance of water so high and still so dangerous?

Pure water does indeed have very high resistivity (different from "resistance"). Reasons water is dangerous around electricity include: Even small amounts of impurities greatly increase the condu...

posted 3y ago by Olin Lathrop‭ · edited 3y ago by Olin Lathrop‭

Answer

#2: Post edited by

Olin Lathrop‭ · 2021-04-11T13:50:51Z (over 3 years ago)

Copy Link

Raw

Markdown

Pure water does indeed have very high resistivity (different from "resistance"). Reasons water is dangerous around electricity include:<ol>
<li>Even small amounts of impurities greatly increase the conductivity of water.
<li>The water that you worry about that might contribute to a shock hazard is especially likely to contain impurities. A flask of highly pure water in a laboratory isn't the danger, its more like a puddle on the floor. Most of the dangerous water (in an electrocution context) is stuff you wouldn't want to drink.
<li>Even small amounts of moisture can make your skin much more conductive.
<li>A little liquid water greatly increases the effective contact area of a conductor touching your skin.
<li>At typical house power voltages, it doesn't take much resistance to cause enough current to hurt, or worse. At 110 V, 110 kΩ allows 1 mA to flow. You'd definitely feel that, making you jerk back involuntarily, possibly hurting yourself in the process. It can also cause muscles to contract uncontrollably. If that happened to your heart muscle for long enough, you're dead. It can also seriously mess up brain signals if running thru the head.
~~And that was all just 110 kΩ with 110 V.~~
</ol>

Pure water does indeed have very high resistivity (different from "resistance"). Reasons water is dangerous around electricity include:<ol>
<li>Even small amounts of impurities greatly increase the conductivity of water.
<li>The water that you worry about that might contribute to a shock hazard is especially likely to contain impurities. A flask of highly pure water in a laboratory isn't the danger, its more like a puddle on the floor. Most of the dangerous water (in an electrocution context) is stuff you wouldn't want to drink.
<li>Even small amounts of moisture can make your skin much more conductive.
<li>A little liquid water greatly increases the effective contact area of a conductor touching your skin.
<li>At typical house power voltages, it doesn't take much resistance to cause enough current to hurt, or worse. At 110 V, 110 kΩ allows 1 mA to flow. You'd definitely feel that, making you jerk back involuntarily, possibly hurting yourself in the process. It can also cause muscles to contract uncontrollably. If that happened to your heart muscle for long enough, you're dead. It can also seriously mess up brain signals if running thru the head. And that was just 110 kΩ with 110 V.
</ol>

#1: Initial revision by

Olin Lathrop‭ · 2021-04-11T13:49:34Z (over 3 years ago)

Copy Link

Raw

Markdown

Pure water does indeed have very high resistivity (different from "resistance").  Reasons water is dangerous around electricity include:<ol>

<li>Even small amounts of impurities greatly increase the conductivity of water.

<li>The water that you worry about that might contribute to a shock hazard is especially likely to contain impurities.  A flask of highly pure water in a laboratory isn't the danger, its more like a puddle on the floor.  Most of the dangerous water (in an electrocution context) is stuff you wouldn't want to drink.

<li>Even small amounts of moisture can make your skin much more conductive.

<li>A little liquid water greatly increases the effective contact area of a conductor touching your skin.

<li>At typical house power voltages, it doesn't take much resistance to cause enough current to hurt, or worse.  At 110 V, 110 k&Omega; allows 1 mA to flow.  You'd definitely feel that, making you jerk back involuntarily, possibly hurting yourself in the process.  It can also cause muscles to contract uncontrollably.  If that happened to your heart muscle for long enough, you're dead.  It can also seriously mess up brain signals if running thru the head.

And that was all just 110 k&Omega; with 110 V.

</ol>

Communities

Post History