Tag: electrocution

Posted in Science & Nature

Thuder And Lightning

Posted on by Jinavie

The best or worst part (depending on your preference) about a dark and stormy night are the majestic flashes of lightning and booming thunder. Most people confuse the two terms, typically using “thunder” to describe both, but technically thunder is the sound produced by lightning, which is the flash of light. Lightning occurs when dense clouds become electrically charged due to the collision of water molecules. As charge builds up, the cloud becomes negatively charged. The negative charge becomes so intense that it begins to push electrons towards the surface of the Earth, creating a positive charge. Electricity always flows from a negative charge to a positive charge through a medium. The intensity of charges causes the air to become ionized (plasma), making it suddenly conductive and allowing the electricity to flow from the cloud to the ground. This is seen as a flash of intense light. As the electricity travels through this channel of air, it superheats the air and causes a massive expansion of air, much like an explosion. This creates an intense shockwave burst, producing a sound that we call thunder.

Lightning is a deadly force of nature. It clocks a peak voltage of somewhere between 30 million to billions of volts – far exceeding the electricity that can be generated by humans. When a lightning bolt strikes a human, it has a mortality rate of between 10~30%. The two effects of lightning on the human body is electrical shock and heat. As lightning flashes over the skin to reach the ground, it leaves a striking pattern known as Lichtenberg figures (see below), showing the path of the electrical breakdown. The intense electrical burst can cause loss of consciousness, arrhythmia or sudden cardiac arrest. The heat generated by the electricity can cause severe burns both externally and internally. It can literally fry internal organs causing permanent damage to the heart, lungs and brain. Neurological symptoms such as amnesia, confusion, sleep disturbance and chronic pain have also been reported. Strangely, there are also reported cases of lightning curing ailments such as blindness, deafness and baldness.

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Because lightning is light and thunder is sound, one can calculate how far away lightning struck using the time between the lightning flash and the sound of thunder. Sound travels at 340m/s, so by multiplying the number of seconds between the lightning and thunder by 340, you can deduce the distance in metres. For example, if you see a lightning strike and then hear thunder after 7 seconds, the lightning must have struck 340m x 7s = 2380m = 2.38km away.

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Posted in History & Literature

War Of The Currents

Posted on by Jinavie

In the late 1880s, a war raged on in the United States – one that is not commonly known by the public. It was a war between two wizards: Nikola “The Wizard of the West” Tesla and Thomas “The Wizard of Menlo Park” Edison.
This war involved no guns or explosives, but centred on something so commonplace that people take it for granted nowadays – electricity. The two scientists/wizards fought to determine whose form of electricity transmission was better.

There are two types of electric currents used for transmission.
Direct current (DC) was used by Thomas Edison, a pioneer of electricity distribution. Before him, electricity was more of a scientific curiosity and was not widely available to the public. DC is a unidirectional flow of electric charge.
Alternating current (AC) was later developed by Nikola Tesla, also a pioneer in the field of electricity. AC is the alternating movement of electric charge as it periodically reverses direction from + to -.

When electricity first became public, the industry standard was DC, as Edison started his company, General Electric. This was incredibly profitable for Edison, whose inventions relied on the usage of DC. For example, his incandescent light bulb was the principal electrical device during the time. Edison further advanced DC technology and heavily advocated it.
Tesla claimed that AC was a much more efficient mode of electricity transmission and tried to convince Edison while working for him. However, Edison ignored him and stated that it was an insane, useless idea. Edison was more an inventor than a mathematician, so he did not understand the theoretical benefits of AC over DC.

AC has the advantage of being able to use a transformer to gain much higher voltage than DC, while losing less power when transmitted. It also allowed easy conversion from low-voltage use, such as lamps, to high-voltage use, such as motors.
Despite this, Edison refused to accept the system and continued to lobby against it. The most famous case is his drastic attempt to defame AC by showing the public how “dangerous” it is.

In 1890, Edison and his company developed the electric chair, which used AC to demonstrate the safety hazards of Tesla’s invention. He did this by arranging the first capital punishment by electrocution. Unfortunately, due to calculation errors, the first shock was insufficient to kill the convict, William Kemmler. The procedure was repeated for 8 minutes, during which the convict was screaming in agony, seizing due to electrocution, and at one point, caught fire. This horrible image is portrayed quite accurately in the film The Green Mile.

Despite this unpleasant event, AC became the standard over time and DC is now only used in labs on certain special applications. Also, the electric chair was adopted as an official method of execution.