Why are there cases where a person touches live wire, gets shocked, and quickly jumps out of it, whereas there are other cases where a person comes in contact with electricity and it ends up “holding” the person until he gets shocked to death. In other words, what determines whether a person gets an electric shock or electrocution?
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How it affects your muscles.
Your muscles are controlled by your brain through electrical signals. If the wrong form of electricity hits your nerves it blocks the signals from your brain and you can’t unclench your hands anymore.
It depends on voltage and frequency if this happens, and also the position of your fingers on the wire. A different form could just cause a quick spasm instead.
The electricity doesn’t hold you, it paralyzes you so you can’t move away.
The strength of the current, basically. A strong enough current will cause involuntary muscle contractions, which then cause you to be unable to let go of the source of electricity. You basically lose muscle control.
If the current is not strong enough, it will just cause you to jerk away.
Electrocution just means a shock that results in death. If the current passes through your heart it will disrupt the electrical signals that control your heartbeat and without immediate medical intervention it will result in death. Whether someone grabs on to and clings on to the wire depends on where the current enters and exits the body; if the current enters the back of your hand you’re obviously not grabbing on to it, but if it enters your palms and exits your elbow it will more likely cause you to grab it. DC power will also cause you to hold on because it’s only flowing in one direction.
A strong enough current will cause your muscles to contract. If you are just brushing something with your fingertips, your fingers will contract away from the source. Touch or grip with your palm, your hand will clamp into a fist and you won’t be able to let go. Touch it with the back of your hand, and your arm muscles will contract so your hand jumps to your shoulder.
The other factor is whether the current is strong enough to travel through your body – watch electricians and you’ll notice that they put one hand behind their back – this stops that hand accidentally touching metal and forming a path that goes thru their heart. If there is no path, or the path goes down the body and leg to the ground, you are more likely to have a smaller, survivable shock.
As the old adage goes, it’s the current that kills you, not the voltage.
Millions of volts can actually be perfectly safe to touch. Van de Graff generators can easily obtain these voltages and people are thrilled by their hand standing on end and fluorescent bulbs lighting.
Why is is safe? Because although it can create very high voltages it can’t sustain a high current. Once current begins to flow the voltage drops very low so that the electron flow is minimal. You can think of it a bit like the Van de Graff generator has a very small amount of electrons with high energy.
Your muscles (including your heart) are very sensitive to current. Your muscles will contract with currents as small as 10 mA, and 100 mA across your heart will cause fibrillation (i.e. death). These are actually relatively small current. Your typical small LED used as a power indicator might have 10mA-20mA flowing through it.
Luckily your skin is a fairly good insulator about 10k ohms dry and 1k ohms wet. Touching that 120VAC outlet while dry will cause ~12 mA to flow which will start to cause muscles to contract. If you are wet, you could get up to 100 mA which is VERY dangerous if the current flows through your heart. We were taught than when dealing with dangerous voltages to use a single hand. The reason for this is if you use two hands and touch a live and neutral wire then the current will flow from one hand to other through your heart (BAD). If you use one hand then the return current will likely try and exit through you foot to ground bypassing your heart.
While 100 mA is sufficient to stop the heart and kill you, that is not the only way electricity can kill you. When large currents flow through your body approximately 1A and greater, they will cause internal burns along the path the electricity follows. These can severely damage tissues leading to death. A typical lightning stroke has about 300 million volts and can consist of 30000 amps (remember your tissue STARTS getting burned around 1A). The good news is if you are dry only about 10,000 of those amps will pass through you. The bad news is 10,000 is quite a bit of current and will burn everything along the path. Even if it doesn’t stop your heart, it will likely kill you from burning you from the inside.
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