Alternating Current (or AC for short)
In an ac circuit, not only does the current change direction periodically; the voltage also periodically reverses. The rate of reversal may range from a few times per second to many billions per second.
Read up on Sine wave AC
All electromagnetic energy has one thing in common: It travels, or propagates, at the speed of light.
The formula for wavelength for Radiowaves is
= 300000000 / Frequency in Hz
= 300/ Frequency in MHz
Memorise this formula as it is the basis of many exam questions.
Next you need to learn about Phase angle
In module 1 you learned the formula for power, Here is an explenation of power in AC circuits.
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To understand inductance you must first learn The fundamentals of Electromagnetism
Magnetic fields are closed fields that surround a magnet. The field consists of lines of magnetic force or flux. It exhibits polarity, which is conventionally indicated as north-seeking and south-seeking poles, or north and south poles for short. Magnetic flux is measured in the SI unit of the weber, which is a volt second (Wb = V s).
The field intensity, known as the flux density, decreases with the square of the distance from the source. In SI units, flux density is represented by the tesla (T), which is one weber per square meter
Magnetic fields exist around two types of materials. First, certain ferromagnetic materials contain molecules aligned so as to produce a magnetic field. Lodestone, Alnico and other materials with high retentivity form permanent magnets because they retain their magnetic properties for long periods. Other materials, such as soft iron, yield temporary magnets that lose their magnetic
The second type of magnetic material is an electrical conductor with a current through it. The needle of a compass placed near a wire carrying direct current will be deflected by the magnetic field around the wire. This phenomenon is one aspect of a two-way relationship: a moving magnetic field whose lines cut across a wire will induce an electrical current in the wire, and an electrical current will produce a magnetic field.
Now on to inducance
Study the following chapter about the L/R time constant
Now would be a good time to learn about Series and parallel circuits using inductors, see the following pages
Charging, Discharging and time constant in Capacitor Circuits.
Now would be a good time to learn about Series and parallel Circuits using Capacitors.
Note the similarities and Differences! Between Capacitor Calculations and the resistance calculations you learned in Module1.