Electrons in Motion
An electric current doesn’t really flow like a stream of water. Instead, electrons pass from one atom to an adjacent atom practically at the speed of light. Of the 92 naturally occurring elements, metals like silver, copper, gold and zinc are the best conductors, meaning their electrons can easily be set into motion and move from one atom to another with little resistance. Other substances like glass or rubber are insulators because their electrons stay in place and halt the flow of an electric current.
Nearly all of the matter surrounding us is made of stable atoms that have an equal number of protons and electrons. An atom of a particular element is defined by the number of protons in its nucleus, ranging from an atom of hydrogen with 1 proton to an atom of uranium with 92. The number of neutrons, also found in the nucleus, is highly variable but mostly stays the same for atoms of the same element.
Balance of Protons and Electrons
An atom with an equal number of protons and electrons is said to have a neutral charge while an excess of electrons means the atom has a negative charge. When atoms of some types of elements are “off balance” in this way they’re called ions. Ions conduct electricity because an electric current can only flow when there is a loss and then a gain of electrons.
Electricity Under Control
Electricity powers up just about everything in our homes, from computers and cell phones to lamps and televisions. Emerging technologies involving solar power and EV’s means that we need environmentally friendly ways to generate large amounts of electricity and transmit it where it’s needed.
Harnessing the power of electrons is possible by varying the components it’s channeled through. A conductor, such as a metal wire, allows it’s electrons to be easily displaced so an electric current flows through it quickly. An insulator performs the opposite task of blocking the flow of current where it isn’t needed or could result in injury. A resistor can be used to slow the current of electricity, lowering its voltage. And a semi-conductor is like a resistor but not exactly.
Semi-conductors are made of an element, such as silicon, that has been mixed with another substance to boost its ability to have its electrons displaced in a controlled way. Some types of semi-conductors encourage a loss of electrons that opens up a “hole” that other free electrons stream toward, creating an electric current. This is the logic behind the photovoltaic cells used to collect solar energy.
The units used to quantify electricity are named after the 18th century scientists who first observed the electromagnetic reactions of positive and negative charges.
AC and DC Current
Electricity can be portable, for example the direct current produced by the batteries that power our cell phones, laptops, and television remotes, or else generated on a much larger scale by power plants transmitting alternating current into our homes and businesses.
Power to the People
During the late 1880’s, the first coal-fueled power plants were built in New York City to generate electricity, about 110 volts of it that could travel just a mile or two along power lines connected to only 50-60 customers. Thomas Edison believed that a source of direct current traveling outward from a power plant at relatively low voltages was a safe and reliable way for Americans to light up his newly invented light bulb. But others disagreed. The problem with Edison’s design was that only a small amount of electricity could travel a short distance before heat loss within the power lines caused the current to be diminished.
The challenge to Edison’s direct current was Nikola Tesla’s invention of AC power. Tesla demonstrated the usefulness of creating a stream of electrons that produced a current by continually changing direction rather than traveling in a straight line. An alternating current is in the form of a wavelength that flows in one direction and then reverses. AC current usually cycles at the rate of 60 times per second, or 60 Hertz, meaning the electric current that flows from power lines into our homes changes direction at a rate of 120 times per second.
The distribution of alternating current differed as well. The problem at the time was finding a way to make electricity accessible to a larger number of customers at a greater distance from where the power was being generated. The friction that was causing heat loss within the power lines was proportional to the amount of current flowing through them; the larger the current, the more heat was lost. And since an increase in current required a higher number of volts to power it through the lines, there needed to be a way to increase both voltage and current, while resistance stayed constant, and then distribute a safe amount of electricity to the customer.
With the invention of the transformer in the mid 1880’s, a large amount of current could be generated at extremely high voltages and delivered to transformers located on the power lines. This is the process in use today. Within the transformer, the voltage is lowered from thousands of volts down to the 120 that safely powers our homes.