(EEM) Forms of Electricity Lesson

Forms of Electricity

Have you ever walked on a carpet and been shocked when you touch a metal object? If so, you experienced an example of static electricity . Static electricity results from the movement of electrons from one substance to another. This transfer of electrons causes the substances to become oppositely charged. This buildup of charge eventually results in a brief discharge.  We feel a shocking sensation and see a spark. A lightning strike is an example of static electricity in nature.   Static electricity is also responsible for the attractive force that causes our clothes to stick together when we remove them from the dryer. Static electricity is unpredictable, difficult to generate and harness so we cannot easily use its energy for our everyday lives.

A more useful form of electricity is current electricity in which electric current flows through a conductor. We can harness this energy and use it to do work. There are two forms of current electricity; direct current (DC) and alternating current (AC). We use both of these forms of electricity to carry out many tasks that we perform each day.

Direct Current

Direct current (DC) moves in one direction and can only generate relatively low voltage. Batteries used in our cell phones, radios, flashlights and cars are the most common sources of direct current electricity. If you look at batteries that are used in small appliances, you will notice that they rarely produce over 10-12 volts. Compare this with alternating current, the other form of electricity that we use in homes and industrial applications, and you will see that much higher voltages can be achieved.

Alternating Current

The most useful type of current electricity is alternating current (AC). Alternating current is the type of electricity in which the direction of flow of the electrical current changes direction many times per second. Alternating Current (AC) electricity powers the appliances in our homes, turns the electric motors of industry and energizes our electric lights. The current in an AC circuit does not instantaneously change direction.   It gradually increases in magnitude until it reaches a maximum in one direction, and then gradually reduces to zero.   Then it gradually increases to a maximum in the other direction, and reduces to zero to start the whole cycle all over again. The number of complete cycles carried out in a second is called the frequency of the AC electricity supply. In the United States the frequency is 60 cycles per second but in other parts of the world the frequency is different. If you travel to Europe, for example, you would need an adapter to run a hair dryer designed for use in the United States.

War of Currents

In the 1880s a battle was waged between Thomas Edison, the inventor of the light bulb, who favored DC current for housing, and George Westinghouse, owner of Westinghouse Electric, who favored AC current. In the beginning, DC current was standard, and Edison did not want to lose his patents. On the other hand, AC was becoming a more reliable and more efficient way to transmit electricity over long distances. The major advantage that AC current had over DC was the ability to change voltages using transformers.

Edison carried out a major campaign to discredit AC current which included spreading misinformation on AC electrical accidents, publicly electrocuting animals (sadly including a circus elephant), and lobbying Congress.   Although Edison did not agree with capital punishment, his desire to disparage AC current led to the invention of the electric chair.

By 1892, General Electric had invested heavily in AC technology, and its use became widespread across the United States. AC power is still used in households today.

Bioelectricity

Another form of electricity that we rarely see or think about is bioelectricity. Bioelectricity is electrical currents that are produced by living organisms. We have electric currents that transmit messages to our brains from our sensory organs, and from our brain to our muscles and glands within our body. The brain itself works by sending electrical impulses from cell to cell, allowing them to communicate with one another. Some organisms, such as an electric eel, can generate large electric fields around their bodies for hunting and protection. Some animals can sense electrical activity from other animals, and they use those to hone in on their prey. Sharks are a good example of animals who can detect prey in this way.

As you can see, we use electricity extensively in our everyday lives. From the time we wake up until the time we go to bed we rely on electrical energy. The lamps that light our way, the television we watch and even our own bodies rely on electrical currents. Our lives would be very different without electrical technology. The next time you listen to your favorite song or talk on your cell phone think about the electrical currents that run those devices and how the world would be much different without electricity.

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