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Effects of Electric Currents on the Human Body

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  • 0:04 What Is Current?
  • 1:07 What Is Too Much Current?
  • 2:21 What Determines…
  • 3:43 What Should You Do?
  • 4:15 Lesson Summary
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Lesson Transcript
Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

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?

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