History of Electrical Circuits
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History of Electrical Circuits Early investigations of static electricity go back hundreds of years. Static electricity is a transfer of electrons produced by friction, like when you rub a balloon across a sweater. A spark or very brief flow of current can occur when charged objects come into contact, but there is no continuous flow of current. In the absence of a continuous current, there is no useful application of electricity. The invention of the battery -- which could produce a continuous flow of current -- made possible the development of the first electric circuits. Alessandro Volta invented the first battery, the voltaic pile, in 1800. The very first circuits used a battery and electrodes immersed in a container of water. The flow of current through the water produced hydrogen and oxygen. The first widespread application of electric circuits for practical use was for electric lighting. Shortly after Thomas Edison invented his incandescent light bulb, he sought practical applications for it by developing an entire power generation and distribution system. The first such system in the United States was the Pearl Street Station in downtown Manhattan. It provided a few square blocks of the city with electric power, primarily for illumination. One classification of circuits has to do with the nature of the current flow. The earliest circuits were battery-powered, which made in a steady, constant current that always flowed in the same direction. This is direct current, or DC. The use of DC continued through the time of the first electric power systems. A major problem with the DC system was that power stations could serve an area of only about a square mile because of power loss in the wires. In 1883, engineers proposed harnessing the tremendous hydroelectric power potential of Niagara Falls to supply the needs of Buffalo, N.Y. Although this power would ultimately go beyond Buffalo to New York City and even farther, there was an initial problem with distance. Buffalo was only 16 miles from Niagara Falls, but the idea was unworkable -- until Nikola Tesla made it possible, as we'll see on the next page. Tesla's Breakthrough Engineer Nikola Tesla, aided by theoretical work by Charles Proteus Steinmetz, came up with the idea of using alternating current, or AC. Unlike direct current, AC is always changing and repeatedly reverses direction. So why was AC the answer to the problem of long-distance power transmission? With AC, it's possible to use transformers to change voltage levels in a circuit. Transformers work on a principle of magnetic induction, which requires a changing magnetic field produced by the alternating current. With transformers, voltages can be increased for long-distance transmission. At the receiving end, the voltage level can decrease to a safer 220V or 110V for business and residential use. We need high voltages for long distances because wire resistance causes power loss. The electrons bumping into atoms lose energy in the form of heat as they travel. This power loss is proportional to the square of the amount of current moving through the wire.
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Transcript of History of Electrical Circuits
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History of Electrical Circuits
Early investigations of static electricitygo back hundreds of years. Static electricity is a transfer of
electrons produced by friction, like when you rub a balloon across a sweater. A spark or very brief flow of
current can occur when charged objects come into contact, but there is no continuous flow of current. In
the absence of a continuous current, there is no useful application ofelectricity.
The invention of thebattery-- which could produce a continuous flow of current -- made possible the
development of the first electric circuits. Alessandro Volta invented the first battery, the voltaic pile, in
1800. The very first circuits used a battery and electrodes immersed in a container ofwater.The flow of
current through the water produced hydrogen and oxygen.
The first widespread application of electric circuits for practical use was for electric lighting. Shortly after
Thomas Edison invented his incandescentlight bulb,he sought practical applications for it by developing
an entire power generation and distribution system. The first such system in theUnited Stateswas the
Pearl Street Station in downtown Manhattan. It provided a few square blocks of the city with electric
power, primarily for illumination.
One classification of circuits has to do with the nature of the current flow. The earliest circuits were
battery-powered, which made in a steady, constant current that always flowed in the same direction. This
is direct current, or DC. The use of DC continued through the time of the first electric power systems. A
major problem with the DC system was that power stations could serve an area of only about a square
mile because of power loss in the wires.
In 1883, engineers proposed harnessing the tremendous hydroelectric power potential ofNiagara Fallsto
supply the needs ofBuffalo, N.Y.Although this power would ultimately go beyond Buffalo to New York
City and even farther, there was an initial problem with distance. Buffalo was only 16 miles from NiagaraFalls, but the idea was unworkable -- until Nikola Tesla made it possible, as we'll see on the next page.
Tesla's Breakthrough
Engineer Nikola Tesla, aided by theoretical work by Charles Proteus Steinmetz, came up with the idea of
using alternating current, or AC. Unlike direct current, AC is always changing and repeatedly reverses
direction.
So why was AC the answer to the problem of long-distance power transmission? With AC, it's possible to
use transformersto change voltage levels in a circuit. Transformers work on a principle of magnetic
induction, which requires a changingmagneticfield produced by the alternating current. Withtransformers, voltages can be increased for long-distance transmission. At the receiving end, the voltage
level can decrease to a safer 220V or 110V for business and residential use.
We need high voltages for long distances because wire resistance causes power loss. The electrons
bumping intoatomslose energy in the form of heat as they travel. This power loss is proportional to the
square of the amount of current moving through the wire.
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To measure the amount of power the line transmits, you can multiply the voltage by the current. You can
express these two ideas using an equation in which I represents current, V represents voltage and P
equals power:
P = V x I
Let's consider the example of transmitting 1 megawatt. If we increase the voltage from 100V to 10,000V,
we can then decrease the current from 10,000A to 100A. This will reduce the power loss by (100) 2, or
10,000. This was Tesla's concept, and from that idea power transmission from Niagara Falls toBuffalo,
and ultimately to New York City and beyond, became a reality.
In theUnited Statesand many other countries, the standard frequencyfor AC power is 60 cycles per
second, or 60 hertz. This means that 60 times a second, a complete cycle of the current flows in one
direction and then in the other. The current flows in one direction for 1/120th of a second and in the other
direction for another 1/120th of a second. The time it takes for one cycle to be completed is called
aperiod, which in this case is 1/60th of a second. In Europeand other areas, the standard frequency for
AC power is 50 hertz.
Electronic circuitsneed both AC and DC. We'll learn about them on the next page.
EDISON VS. TESLA
Thomas Edison was a brilliant and intuitive inventor. However, his limited schooling, especially in
mathematics, kept him from a true understanding of the theory behind ACelectricity.He understood DC
well enough, but AC was, strangely, a bit beyond his grasp. He strongly opposed the idea of using AC for
long-distance power transmission, but AC gradually replaced DC as the primary means of electric power
transmission.
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