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Human Physiology and Electric Shocks | KnowledgeisKey

Summary

Have you ever had an electric shock? Chances are, you have in some way or another. Most people will have fond memories of shuffling their feet across the floor to give someone an unpleasant shock of static electricity, then running away in a fit of laughter. However, some unfortunate people may experience a much nastier electric shock, and even end up in hospital.

By, Ricky Goacher | Date: 09/12/2017 | Updated: 18/01/2018

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Fun Facts:

A US Navy sailor earned himself a Darwin award by electrocuting himself with a 9 volt battery in an attempt to measure his bodily resistance from thumb to thumb with two probes, which he accidentally pricked himself with in his excitement, disrupting the electrical regulation of his heartbeat and killing him.

human evolution

A US Navy sailor earned himself a Darwin award by electrocuting himself with a 9-volt battery in an attempt to measure his bodily resistance from thumb to thumb with two probes, which he accidentally pricked himself within his excitement, disrupting the electrical regulation of his heartbeat and killing him.

Have you ever had an electric shock? Chances are, you have in some way or another. Most people will have fond memories of shuffling their feet across the floor to give someone an unpleasant shock of static electricity, then running away in a fit of laughter. However, some unfortunate people may experience a much nastier electric shock, and even end up in hospital.

It's important to understand the effects of electricity on the human body and how to protect yourself. In this article, we are going to cover the dangers of working with electricity and explain some of the electrical safety practices which are used to minimise the risk when working with electricity.

If you're not already familiar with terms such as voltage, resistance, and currents, which are crucial to understanding Ohm's law, have a look at the video below:

Ohm's law describes a relationship between electric current, voltage and resistance. It states that if you increase the voltage through a circuit with a fixed resistance, the current will also increase. The formula for Ohm's law can be written in three simple derivative equations, in which R is resistance measured in ohms, V describes voltage measured in volts, and I stands for current measured in amps.

  • R=V/I (resistance equals voltage divided by current)

  • I=V/R (current equals voltage divided by resistance)

  • V=IR (voltage equals current multiplied by resistance)

What can an electric shock do to your body?

Electrician maintaining electrical cables

In the human body, there are current pathways that will commonly allow current to pass through them. This puts humans at risk of electric shock, as the body can conduct electricity through these current pathways. Examples of these pathways include:

  • Blood - The water in the blood can conduct electricity. This can harm the heart and even stop it from beating! However, this can only happen if a large enough current flows through the pathways.

  • Hands - The moisture of the skin will affect the risk of shock. For example, the palms of the hands can get sweaty and can conduct electricity through the skin because it has less resistance than dry skin.

Different amounts of current flowing through the current pathways will have different effects on the human body.

  • 1mA=0.001A - The body would feel a small pinprick feeling/shock

  • 10mA=0.010A – This is enough to make the muscles in the body expand and contract. This amount of current would also make it possible for you to be unable to let go of whatever you are holding.

  • 1000mA=1A- This the lowest amount of current that is enough to stop the heart.

Most of the appliances we use today have more than 1 amp of current running through them, which means they can be dangerous, and we must use them safely. A safe level of DC voltage to work with would be about 40 - 50 volts, as a person can begin to feel a shock at 50-60V.

Areas electricity can affect in the body

Human phsyology diagram

Electricity can get through the skin of the human body, but only if it has a high enough voltage. However, It has more conductance if the skin is wet. A shock through the wet skin can damage the veins. For this reason, you are advised never to handle electrical objects with wet skin. This is advice you should take seriously.

More current can flow through if there is less resistance. The resistance of dry skin may be as high as 100,000 Ω(Ohm's), but the resistance of wet skin is 1000Ω. Cracked or burnt skin has a resistance of about 500Ω which means, when a person is electrocuted the resistance in their skin drops as it is damaged.

In the mouth, you can get an electric shock through the saliva because it is more conductive. This is because it has less resistance due to the moisture, so more current will flow through it.

Nerve impulses are electrical in nature, but an electric shock of a high voltage can “scramble” the system. This can cause the muscles to contract and other unpleasant side effects. Let's take a look at what electricity can do to the body.

If the electrical current is between 1 - 5mA it should have no lasting effects, If it was between 10mA-20mA the muscles contract. E.g., grabbing the open circuit and not being able to let go and electrocute themselves. 75mA-200mA causes severe burns because the electrons are colliding into the muscle cells, damaging the muscles. If a current is high enough it can be life-threatening, as it can cause fibrillation of the heart.

Above 200mA the muscle contractions become so intense that the heart muscles cannot move at all, causing the heart to stop. The heat from the electricity (electrons colliding) travelling through the body damages and denatures the nervous system cells.

The brain can also be affected by electric shock as it receives electrical impulses from the nervous system. The scrambled impulses and heat from the electron collisions can denature cells in the brain causing brain damage.

How electricity can enter and exit the body

The effects of a shock can depend on where the electricity entered the body and where it exits it. If the current passes from one side of the body to the other, it will most likely pass through your heart on its current pathway, making it more dangerous than a shock entering in the left arm and exiting through the left foot.

It can also depend if you’re in contact with the ground. Electricity is always trying to earth itself. For example, travelling from your leg to the earth. A typical example is pigeons sat on high voltage electrical wires, they do not receive an electric shock, but why? This is because there is no current pathway through the pigeon that will let the electricity earth itself because they are not physically touching the ground.

First aid in case of an electrical injury

Pulse trace, heart rate monitor

The first thing you must do is separate the person from the source of the electricity as quickly as possible, the longer the exposure, the more damage is done. The best way to do this is to turn the power source off. Failing to do that, find an object to help separate the person from the source, this object must be none conductive, however.

An ideal object would be something like a wooden broom. You must NEVER touch a person who is receiving a shock, or you may also be on the receiving end.

Once separated from the source, immediately assess the severity of the situation. When a person is electrocuted, in the worst case scenarios, an electric shock may lead to a condition known as electroporation, this is where cells within the body rupture, causing tissue death.

If the person is now unconscious, you must phone an ambulance immediately; it is essential that trained professionals arrive ASAP to administer first aid to the victim.

While you are waiting for an ambulance, it is vital that you stay with the victim and try to wake the person and assess the level of electrical injury. Ask them things like their name, where they are from, and how they are feeling. You must never try to move the person unless they are still in possible danger.

There are many variables which can determine what injuries a person might sustain. These variables include The voltage of the source, the resistance of tissues, i.e., if the tissue was wet or damaged, the type of current AC or DC, the amount of current (voltage and resistance) and the pathway which the electricity takes through the body.

For example, low voltage electricity will most likely not cause significant harm; however, some people have experienced a variety of side effects after being on the receiving end of a mild shock, a few examples of these are; a headache after an electric shock, tingling and muscle pain.

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