Why Doesn’t Static Electricity Kill You?
Static electricity has a high voltage, so why are those electric shocks merely annoying instead of deadly? Ask Science explains
Lee Falin, PhD
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Why Doesn’t Static Electricity Kill You?
An intrepid listener wrote in with this question about my episode on static electricity:
“I was wondering why the thousands of volts discharged from static electricity is just a painful shock and but not more harmful? I understand the discharge can damage computer electronics buy why doesn’t it harm us also?” – Chris
Well Chris, that’s a great question. Let’s unravel this shocking mystery.
The Law of the Electric Land
There are 3 things people typically consider when thinking about how dangerous electricity is:
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Voltage (measured in volts) tells you how much force will be used to push through your body.
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Resistance (measured in ohms) tells you how strongly your body will resist those electrons being pushed through it.
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Current (measured in amps) tells you how many electrons will flow through you each second.
Back in 1827, a man named Georg Ohm published an early version of an equation that related these 3 things together:
Voltage = Current x Resistance
Unfortunately many scientists weren’t very impressed with this law when it was published. The German minister of education is infamously quoted as saying about Ohm that “…a physicist who professed such heresies was unworthy to teach science.” Others called Ohm’s work “a web of naked fancies” and “the result of an incurable delusion.”
Eventually Ohm was vindicated, he and his law became world famous, and had a statue built in his honor at the school where he was a professor of physics. So let that give you some comfort the next time one of your science teachers makes disparaging remarks about your homework..
I’ve Got the Power
When we’re trying to quantify how dangerous electricity is, people generally don’t look at how strong the electrical force (aka, the voltage) is. Instead, they look at how much electricity charges through you each second (the current) to determine how harmful it is.
You might have heard people say something like “It isn’t the volts that kill you, it’s the amps.” This is another way of saying “It isn’t the voltage that kills you, it’s the current.” However the current is only part of the story. In order to really know how dangerous a source of electricity is, you have to consider the amount of electricity that source has available, which we call electrical charge:
Electrical charge (measured in coulombs) can be thought of as the quantity of electrons available to flow.
Static electricity has a high voltage, but a very low electrical charge. So while those electrons want to tear across your body like there’s no tomorrow, there just aren’t enough of them to do any damage.
On the other hand, the electrical socket in your home has a relatively low voltage, but an unlimited amount of charge, making it much more dangerous than the high voltage of static electricity.
Being Thick Skinned
Normally the human body has a pretty high resistance to electricity thanks to our skin. However, certain things can significantly lower our resistance, such as when we’re wet, or when our skin is punctured or burned.
This is why an electrical source with high voltage and an unlimited current is particularly dangerous, because the high voltage burns your skin, allowing the current to more easily flow through your body.
Conclusion
So now you know why static electricity doesn’t kill you; despite having extremely high voltage, there just isn’t enough electrical charge available to do any damage. Of course this only refers to direct damage from static electricity. Electrostatic discharge can still cause you trouble if it ignites something combustible, such as happened with the Hindenburg disaster.
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