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What Is Radio Frequency Induction? Part 2
In the previous article, Part 1, we discussed the inducing of a current into a coil of wire from a changing magnetic field. It actually did not need to be a coil of wire. Current is induced into a single run of straight wire as well. The coil allowed the induction process to be much more effective.
In elementary school you probably saw a science experiment where a magnet was made from a an iron nail, a coil of wire, and a battery. The current flowing through the coil of wire, somehow magnetized the iron nail. If you think about this, we have just the opposite as was discussed in Part 1.
In Part 1 we had a magnetic field causing a flow of current in a wire. Here we have a flow of current in a wire causing a magnetic field to be produced. So we see that this induction process is reciprocal. We can start with a magnetic field and cause a flow of current to be produced, or we can start with a flow of current and cause a magnetic field to be produced.
Let's take a simple everyday example. We will not use RF energy in this example. We will use the magnetic fields associated with the A.C. power lines. We'll move to RF after that.
Let's take a portable tape recorder. Turn it on and start recording. Hold the tape recorder near an electric fan motor for a moment. Now play back the audio that you recorded. You will probably hear a hum in the tape recorder recording when you brought the tape recorder near to the electric fan motor. What is happening?
- Current is flowing in the fan motor.
- The flow of current in the fan motor is causing a strong magnetic field to be produced in its immediate vicinity.
- That magnetic field is inducing a flow of current in the tape recorder audio circuits. That current is 50 or 60 Hz (Hz = cycles per second) and that low frequency is heard as hum.
RF induction is the very same. The frequencies are much higher than the 50 or 60 Hz of the A.C. power lines but the physics of what is happening is precisely the same. Part 3 of this series will discuss the countless ways that induction surrounds us in this modern world.
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