ELECTROMAGNETISM
Magnetic Induction, Inductance, AC and LC Circuits
Alternating and Direct Currents
LEARNING COMPETENCIES
Compare and contrast alternating current (AC) and direct current (DC).
Before comparing and contrasting alternating current (AC) and direct current (DC), it is best to make a review on the basics.
An electric current is a flow of electric charge. In electric circuits, this charge is often carried by moving electrons in a wire.
An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire.
Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, solar cells, and commutator-type electric machines of the dynamo type.
Simple direct current (DC) circuit
Solar cells
Battery
BIG IDEA
Alternating Current (AC) flows in a back-and-forth motion
Alternating current (AC) electricity is the type of electricity commonly used in homes and businesses throughout the world. While direct current (DC) electricity flows in one direction through a wire, AC electricity alternates its direction in a back-and-forth motion.
Photo credit to www.windows2universe.org.
AC electricity is created by an AC electric generator, which determines the frequency. What is special about AC electricity is that the voltage can be readily changed, thus making it more suitable for long-distance transmission than DC electricity. But also, AC can employ capacitors and inductors in electronic circuitry, allowing for a wide range of applications.
At this point of the lesson, the teacher may want to ask the learners these questions:
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What is the difference between AC and DC electricity?
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Why do we use AC instead of DC?
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What are advantages of AC electricity?
Electrons have negative (−) electrical charges. Since we know that opposite charges attract, they (electrons) will move toward an area consisting of positive (+) charges. This movement is made easier in an electrical conductor, such as a metal wire.
With direct current (DC), connecting a wire from the negative terminal of a battery to the positive terminal will cause the negatively charged electrons to rush through the wire toward the positive charged side. The same thing happens with a DC generator, where the motion of coiled wire through a magnetic field pushes electrons out of one terminal and attracts electrons to the other terminal.
With an alternating current (AC) generator, a slightly different configuration alternates the push and pull of each generator terminal. Thus the electricity in the wire moves in one direction for a short while and then reverses its direction when the generator armature is in a different position.
Many electrical devices—like light bulbs—only require that the electrons move. They don't care if the electrons flow through the wire or simply move back-and-forth. Thus a light bulb can be used with either AC or DC electricity.
Advantages of AC Electricity
The major advantage that AC electricity has over DC electricity is that AC voltages can be readily transformed to higher or lower voltage levels, while it is difficult to do that with DC voltages.
Since high voltages are more efficient for sending electricity to great distances, AC electricity has an advantage over DC. This is because the high voltages from the power station can be easily reduced to a safer voltage for use in the house.
Changing voltages is done by the use of a transformer. This device uses properties of AC electromagnets to change the voltages.
This video serves an alternative source of information about alternating and direct current.
As stated on the introduction part of the video, the author wanted to differentiate alternating current from direct current. Also, the author aimed at analyzing the pros and cons of AC and DC. The video also provides symbols and diagrams describing how direct and alternating currents work.
Mahl, C. (2014, January 15). AC vs. DC. Retrieved November 25, 2015, from https://www.youtube.com/watch?v=BcIDRet787k
It would be easy to leave AC as a slightly mysterious version of the direct currents that you deal with in simple DC experiments, and to suggest that detailed studies belong to later work in engineering. But AC is our standard form of supply. It is far more economical in distribution than DC because of the efficiency and simplicity of transformers.
You probably live in a house or apartment with sockets that deliver AC. Your radio, television and portable phone receive it, using circuits. So AC signals are almost everywhere. And you can't escape them, because even the electrical circuits in your brain use capacitors and resistors.