The amount of current through a body is equal to the amount of voltage applied between two points on that body, divided by the electrical resistance offered by the body between those two points. This is what brings about the danger of high voltage, which means potential for large amounts of current through the body, which can injure or kill. But the more resistance a body offers to current, the slower the electrons will flow for any given amount of voltage.
Basically, just how much voltage is dangerous depends on how much total resistance is in the circuit to oppose the flow of electrons. Body resistance is not a fixed quantity — it varies from person to person. It also varies depending on how contact is made with the skin. For example, is it from hand-to-hand, hand-to-foot, foot-to-foot, hand-to-elbow, etc.?
Sweat, being rich in salts and minerals, is an excellent conductor of electricity. So is blood, which has a similar content of conductive chemicals. Contact with a wire made by a sweaty hand or open wound will offer much less resistance to current than contact made by dry skin. Individuals have been electrocuted by appliances using ordinary house currents of volts and by electrical apparatus in industry using as little as 42 volts direct current.
The true measure of a shock's intensity is within the amount of current forced though the body, not the voltage. Meaning, any electrical device used on a house wiring circuit is able to, under certain conditions, transmit a fatal current. Currents above mA, though they can produce severe burns and unconsciousness, do not normally cause death if the victim is given immediate attention. Resuscitation, consisting of artificial respiration, will usually revive the victim. Overall, electricity's effect on the body depends on the specific path the current takes through the body, and on the characteristics of the individual's body.
A large amount of current can kill a person by cooking the insides. We're all conscious of the dangers of electricity. We know that 3-volt batteries are safe, but outlets are dangerous enough that they should be covered in order to protect toddlers. We also know not to use a hair dryer in the bathtub.
But why? How does electricity actually hurt people? Volts and amperes amps are properties used to describe most simple electrical phenomena in the world around us. Amperage A is a measure of current flow, i. One amp is about 6 million trillion electrons per second. This flow of electrons is what actually causes tissue or nervous system damage. All those electrons passing through a body either heat and burn tissues or interfere with essential electrical signals, such as those that cause the heart to beat.
The latter phenomenon is why an electrocution above a certain amperage will cause your muscles to clench and make it impossible for a person to let go of the current source. Being physically unable to let go of a live wire is called tetanic contraction. Voltage V is how strong the "urge" is for the current to flow. Voltage is the push on the electrons.
A rough analogy is that current is like water molecules, and voltage is like a slope. The steeper the slope, the more the water molecules wants to flow down it. Zero voltage between two points is like a plateau and, hence, there is no current flow. An object's electrical resistance measured in ohms limits the amount of current that any voltage can drive through it.
The stronger the resistance, the more voltage you need to push the same amount of current. The body's natural resistance is its defense against electricity.
Internal tissue has a low resistance compared to the skin. Thus, small shocks are not a problem, but once the skin is breached, the rest of the body is defenseless.
That explains why a 3-volt battery is harmless, but Old Sparky was rather deadly.
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