Most of you must have experienced personally or have heard about electric shocks and also know how lethal it can be in some cases. Its something which are taught and made aware of to the children from a very young age. The knowledge about electric shocks is also a very important lesson when it comes to personal safety and first-aid.
Multiple warning boards can be seen at places that read “CAUTION- High Voltage” which is a clear sign to us that its lethal for us and we must not try to mess around at such areas. Time to talk about it with a different perspective
Why do you get a Shock?
When you come contact with an electrical energy source you get a shock. Electrical energy flow through you body and it leads to a shock. Basically, electrons flow through your body especially via blood leading to a current.
But, here is the catch, unless and until in general you are grounded you don’t get a shock. This is because you are safe till you are insulated as this doesn’t give a complete circuit/path for current to flow.
The Half True Reason
Coming back to the warning boards, it reads only about the voltage, why? The answer may come as the resistance of a human body is almost fixed so a high voltage will lead to a flow a high current through the body as per the Ohm’s Law.
Voltage= Current x Resistance
True, and self-explanatory but its incomplete. The word incomplete here doesn’t mean that the above reason is a hoax, all I mean to say is the reason is absolutely true but it is not the complete reason.
The complete reason, it is the current which is alone solely responsible for electric shocks.
Why it is the Current and not the Voltage?
It is a very common argument that its the voltage that leads to current so its the voltage that matters. But, we must understand that current and voltage are two independent physical quantities.
We all know, along with Ohm’s law, voltage and current are also relate to power.
Power = Voltage x Current
So, for a given power we can have a very high voltage and a low current, also we can have very high current and a low voltage.
So, here what do you think does high voltage really mean high current? Well not always. One very good example of this is the Tesla Coils.
What is a Tesla Coil?
Tesla coil is an electrical resonant transformer circuit. It is a radio frequency oscillator that drives a transformer to produce high voltages at low currents. More advanced designs use transistor or thyristor switches to drive the resonant transformer. They can produce output voltages from 50 kilovolts to several million volts for large coils. These days it is used for entertainment and educational displays, although small coils are still used today as leak detectors for high vacuum systems.
You can have the Tesla coil at very high voltage at a fixed power output (in the safe-zone obviously), and bring your closer to it slowly. What will you observe is that there is a spark between the Tesla Coil and your finger but you barely feel anything.
First of all, a current does flow through your body (quite evident from the spark). This current is developed because of the dielectric breakdown of the air between your finger and the Tesla coil. The voltage is so high that it ionises the air to an extent that it leads to the dielectric breakdown. But, the current is significantly so low that it barely hurts you. This also the principle behind the working of the Plasma Globe.
What is a Plasma Globe?
At the centre of a plasma ball is a large alternating voltage, typically a few kilovolts oscillating at around 30 kHz. The low density of the gas in the globe (often neon) makes discharge significantly more favourable than it is in air at atmospheric pressure (the breakdown voltage of air which causes sparks from a Van de Graaff generator, for example, is 30,000 V/cm, whilst this can create arcs many centimetres long with just a few thousand volts). These fronds of plasma make their way from the centre of the globe to the edge, in a bid to reach earth. Creating an enhanced path to earth by touching the globe increases the strength of the discharge, which is why the arcs are attracted to your hand if you touch the globe.
Video Courtesy – ” Plasma Channel “
So, now I think you know that it is only the current which is responsible for an electric shock.