Your body is very sensitive to the effects of electric currents, and even small amounts of current can cause serious problems and even death. In this lesson, learn more about current and the effects it can have on your body.
What Is Current?
When you turn on a light switch, you expect the lights to come on, right? Have you ever thought about exactly what is going on in the light to make it come on? If you could make yourself really small and get inside the bulb, you would see lots and lots of tiny charged particles, called electrons, moving through the wires and filament of the bulb. As the electrons move through, they transport energy, and this electrical energy is transformed into other kinds of energy, like light and thermal energy, by the bulb.
This flow of charged particles is known as current, and it's what powers all electrical devices, from light bulbs to computers to refrigerators! Electric current is measured in units of amperes (A), and it doesn't take much current to hurt or even kill you.
Your body is also generating currents all the time as well. Your muscle cells, including the cells in your heart, contract in response to tiny electrical currents that are generated by your nervous system. Because these cells are sensitive to even small amounts of current, any additional current that passes through your body can disrupt this system, causing uncontrollable muscle contractions and even causing your heart to stop in many cases.
What Is Too Much Current?
Electric current in the human body is dangerous for two primary reasons. First, it disrupts the normal operation of your nervous and muscular systems, causing severe muscle contractions. Second, just like in the light bulb, when current passes through your body, it's transformed into thermal energy. This can cause serious burns, both inside your body and on your skin.
Exactly how much current does it take to cause these serious problems? Not much!
Because your body is very sensitive to the effects of electric current, even small amounts of current can be very dangerous. Currents of about 10 mA can cause a very painful shock and muscle contractions so severe that you cannot let go of whatever is shocking you. Every second the current continues to pass through you, more heat is generated and the damage to your body increases, so the inability to let go can cause some serious problems.
At currents ranging from 20-100 mA, the muscles that allow you to breathe become paralyzed, and above 100 mA, your heart will cease beating rhythmically. It will instead quiver in an uncoordinated way, known as ventricular fibrillation, that is fatal if not corrected within a few seconds. Currents above about 100 mA are almost always fatal unless immediate medical attention is provided, and death can occur at even lower currents depending on how long the current is present.
What Determines Current Amount?
The amount of current passing through a human body depends on two things: the voltage supplied by the source and the electrical resistance of your body. Voltage can be considered the force pushing the current, and resistance refers to the ability of something (in this case, your body) to oppose, or resist, that current.
Sometimes people receive a fatal shock from small handheld devices that operate at a voltage less than 100 Volts, and sometimes people survive being struck by lightning, where the voltage between cloud and ground can reach 100 million volts! How is this possible?
While voltage has to be involved to establish a current, the amount of voltage applied is not the reason behind the damage sustained to a body. Instead, it's the current that is dangerous. Consider this: if you have a high voltage but low current, it's just a big force pushing a small amount of charge through you. That's not so damaging. But if you have a high current, regardless of the voltage, that's a lot of energy running through your body!
Your body's electrical resistance to current is also important in determining how much current passes through you. Your resistance depends on many things, including the area through which the current flows, the amount of your body that's in contact with the source of the current, and whether or not you are wet or dry. Dry skin has a very high resistance, but this resistance drops significantly if your skin is wet. This is why fatal electrocutions often occur near water. Given the same source voltage, much more current will pass through you when your skin is wet.
What Should You Do?
If you see someone who is being shocked by an electric current, what should you do? First, don't touch the person directly. If you touch a person who has current passing through their body, then you may get shocked, too. Try to use a non-conductive material like a piece of wood or plastic to separate the person from the object that's shocking them. This is especially important because the muscle contractions caused by the current may prevent the person from letting go on their own. Serious electrical shocks require immediate medical assistance, so contact a hospital or other emergency workers right away to get help!
Let's take a couple of moments to review what we've learned. Electric current is the flow of charged particles through an object. The amount of current that flows depends on the voltage, or the force pushing the current. It specifically depends on the voltage being applied and the resistance, or the ability to oppose the current, of the object. When current flows through the human body, it can cause a lot of problems. Currents as low as 10 mA can cause severe muscle contractions and burns, while currents of 20 mA or greater can cause paralysis of the muscles that allow you to breathe. Any current greater than 100 mA can cause your heart to stop beating normally and enter ventricular fibrillation. This condition is fatal within seconds if it's not reversed.
Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.