Tesla

Nikola Tesla was a was a Serbian American inventor, electrical engineer, mechanical engineer, and physicist best known for his contributions to the design of the modern alternating current (AC) electricity supply system.

Among his numerous innovations, Nikola Tesla dreamed of creating a way to supply power to the world without stringing wires across the globe. Tesla, having a reputation in popular culture as an archetypical mad scientist, came very close to achieving this dream when his experiments led him to the invention of the Tesla Coil.

How exactly was the Tesla Coil important? Simply put, it was the first system that could wirelessly transmit electricity.  As such, the Tesla coil was, though accidental, a truly revolutionary invention and was used by early telegraphy and radio antennas.

A Tesla coil consists of both a primary coil and secondary coil, each having its own capacitor.  Capacitors are capable of storing electrical energy much like batteries do. “The two coils and capacitors are connected by a spark gap — a gap of air between two electrodes that generates the spark of electricity”.  An outside source hooked up to a transformer powers the whole system. Essentially, the Tesla coil is two open electric circuits connected to a spark gap.

A Tesla coil needs a high-voltage power source. A regular power source fed through a transformer can usually produce the thousand volts necessary to power up the coils.  The transformer is necessary as it converts the low voltage of main power into high voltage.

How it Works:

A power source is hooked up to the Tesla coil’s primary coil and its capacitor acts like a sponge as it soaks up the charge. “The primary coil itself must be able to withstand the massive charge and huge surges of current”.   Due to this reason, the coil is usually made out of copper, widely known as a great conductor of electricity.  After enough time, the capacitor builds an immense charge that the air resistance in the spark gap between the two coils is broken. Shortly after, the current flows “out of the capacitor down the primary coil and creates a magnetic field”.  This can once again be compared to a sponge when it gets squeezed out, releasing all it had soaked up.

The amount of energy makes the magnetic field created in the space between the two coils collapse, thus generating an electric current in the secondary coil. At this point, the voltage zipping through the air between the two coils creates sparks in the spark gap. “The energy sloshes back and forth between the two coils several hundred times per second, and builds up in the secondary coil and its capacitor”. Eventually, the charge in the secondary capacitor gets so high that it breaks free.

In a perfectly designed Tesla coil, when the secondary coil reaches its maximum charge, the whole process should start over again and the device should become self-sustaining. In practice, however, this does not happen. The heated air in the spark gap pulls some of the electricity away from the secondary coil and back into the gap, so eventually the Tesla coil will run out of energy. This is why the coil must be hooked up to an outside power supply.

The principle behind the Tesla coil is to achieve a phenomenon called resonance. This happens when the primary coil shoots the current into the secondary coil at just the right time to maximize the energy transferred into the secondary coil.

Current Work:

WiTricity and Doctor Katie Hall have made remarkable leaps in the field of wireless energy as she aims to freely transfer power without any wires.  Doctor Hall states that they do not intend to put electricity in the air, but instead create a magnetic field.

WiTricity builds a “Source Resonator,” a coil of electrical wire that generates a magnetic field when power is attached.  If another coil is brought close, an electrical charge can be generated.  No wires required.  “When you bring a device into that magnetic field, it induces a current in the device, and by that you’re able to transfer power,” explains Dr Hall.

The goal is to add these magnetic fields to homes and have all electrical devices charge or be turned on without the necessity for  wires.  Hall assures that the magnetic fields used to transfer energy are “perfectly safe” — in fact, they are the same as the ones used in Wi-Fi routers.

“If all goes to WiTricity’s plans, smartphones will charge in your pocket as you wander around, televisions will flicker with no wires attached, and electric cars will refuel while sitting on the driveway.”

Sources:

http://theoatmeal.com/comics/tesla

http://www.pbs.org/tesla/

http://www.reformation.org/nikola-tesla.html

http://www.cnn.com/2014/03/14/tech/innovation/wireless-electricity/

http://www.realclearscience.com/articles/2014/01/29/how_tesla_coils_work_108474.html