Answer:What your teacher was referring to was surely the slow brain waves that indeed exist inside all our brains. We cannot hear them because they are electrical oscillations and not sound.

Your teacher said: Some of them could be heard... I suppose what he meant was the different frequencies of those brain waves. Firstly, the really slow ones are well below anything we could hear as sound. They can be as low as 2 or 4 cycles per second. We express this as 2 to 4 Hz. ('Hertz') The lowest sound we could recognise as a musical note (really low bass that is, maybe from a pipe organ in a large cathedral or the large drum in an orchestra) has 16 Hz. The higher ones may reach up to 35 Hz and higher. Let me say it again, they could be heard if there were sound. They are not sound, but electrical oscillations.

All these brain waves can be heard. What is needed for this is an apparatus with electronic sensors that are put on our skull. They pick up those oscillations which are amplified and fed into a loudspeaker or head phones. As the frequencies are mostly below our auditory spectrum they can be modulated (mixed) with 'white noise' and what we hear then sounds similar to an old steam locomotive in the distance. It is interesting to listen to your own brain waves and with practice even be able to switch them on and off.

There is one problem with this: The oscillations from your brain at the outside of the skull are so weak that advanced technology is needed to get a clear signal. Stray noises from all those outside sources around us easily swamp what we want to hear.

What frequencies are generated depends on our state of mind. The most famous frequency is the "Alpha" wave, a frequency of between eight and twelve Hz. The untrained person may produce this at will by putting him/herself into a state of relaxation and reflection and have the eyes closed. Some people use this exercise for meditation. When we are asleep, the frequency goes down to maybe 3 or so Hz while during our busy daily activities they are well above the alpha wave.

I hope that helps you understand one of the mysterious ways of what our brains are up to, without any awareness on our part.

Peter.

The following are excerpts from a much longer letter from WMc.

Question: I read with interest your 10 Junior Electronics fact sheets, which an old college friend found while searching the Internet as a follow-on to a discussion we had about a PTO-driven generator that I had recently purchased, which led into a further discussion of how electricity "works".Unfortunately I did not find all that I wanted to know in those 10 sheets.

Answer: Yes, these first pages out of a collection of over one hundred are in the first place for the younger generation. From experience I know that if you bore them with too much theory, they are likely to lose interest. For this reason I went very soon into practical, hands-on material. Once they have got a good handle on the technology they are more apt to learn the in-betweens when the time comes.

Question: Are the electrons actually moving?

Answer: Electricity, in spite of all the collected wisdom over the last 200 years, is still a mystery in many ways. But what the experts say is that the outer electron layers of the atoms in certain materials (metals, certain liquids etc.) are able to move from atom to atom. Under the influence of an energy which we call 'voltage', they are pushed in a certain direction. So the answer to your question is Yes. In my Fact Sheet 31 which is also on the net under: "Which way does the current flow?" this is taken a little further.

Question: what it is that a generator generates....

Answer: The generator creates this electrical potential called voltage. It depends on the mass (so-to-speak) of the generator and its internal resistance, how much current it can produce, e.g. how many electrons it is able to push around the network.

Question: ...you end up with a pile of dead electrons in your light bulb :-)

Answer: I'm still recovering from compulsive fits of laughter. I have never heard that before and can well imagine having an electron cemetery where people come with buckets full with their now dead electrons and put them to eternal rest.

Question: Even more confusing to us was the concept of alternating current...

Answer: You may have noticed that I often explain happenings in the field by analogies. We can SEE water and imagine how it flows. We can NOT see electrons, only detect what they DO. Now imagine a moat, that river-like ring of water around a castle. On one side there is a man with a paddle. He pushes the water in the clockwise direction around the castle. On the other side there is a water wheel. The energy is transferred from the man to the other side and so the wheel turns. In electricity that would be DC. Now take AC. The man pushes the water one second in the clockwise direction, the next second in the anticlockwise direction, then back clockwise and so on. So the energy's POLARITY alternates from one direction to the other and back, continuously. In fact in power distribution it changes 60 times a second in the US, in other countries 50 times a second. The reasons for AC are too involved to explain here, but in a nutshell: DC cannot be transformed. AC can. It is here where the otherwise famous Thomas Edison made a fool of himself. AC, suggested by Nicola Tesla, won the day and is used now all over the world for distributing power and other things.

Question: ...grab my 17, 13, and 8 year-old boys...

Answer: In many countries this knowledge is not high on the teaching agenda. I hope it is better over there. After all, we live in a highly technological age and electronics is one of the more interesting fields. In all human endeavor, imagine where electricity and electronics is NOT used? I think it should be taught to the next generation - at least the fundamentals. That's by the way.

Finally, thanks for your note. I'm always glad to hear from visitors to my page. I hope the above helps.

Regards

Peter.

Question: Our teacher talked about resistance and how to measure it. I could not really follow what he said. I am confused. Can you explain why we have to know what resistance is about and how we measure it?

Answer: Sometimes it is important for us to know the resistance of an electrical component or gadget. This could be a resistor, a transformer, a hot plate or maybe a long lead.

Here are just a few examples where the measurements of the resistance is needed: A resistor (component) may have its value rubbed off and we have to measure it to find out what value it has. A transformer that is supposed to reduce the 115 or 240 'VAC' (which means Volts, Alternative Current) down to a safe 9 V or so but has no data written on it. If we measure the resistance of its two windings we will find immediately the primary (the input) with its much higher resistance reading than the lower which is the secondary. Moreover, if the value of a winding is infinitely high, we know at once that there is an open circuit somewhere. If a long lead is supposed to carry a heavy current we will have to know how many ohms it has. Only then can we calculate the losses that occur in that circuit.

One way of measuring R is to use a known exact and constant voltage. Constant means the source of the voltage, a battery or a power supply, must have a LOW IMPEDANCE. (otherwise the voltage may vary with different loads.) Now all we have to do is to find out how much current is flowing through the unknown component and calculate according to Ohms Law: Voltage over current equals Resistance. For instance, if our voltage comes from a fully charged car battery delivering 12 V, and the current flowing through the component is 60 mA, then the resistance of that component will be 12 divided by 0.06 = 200 Ohms. Note that we convert the mA to A. In Ohms formula, Voltage, Current and Resistance are always expressed in either Volts (not millivolts or kilovolts) and Amps (not milliamps) and Ohms (not kOhms or MOhms), otherwise we get a false reading.

If we have a multimeter handy, the matter is much simpler. The Ohm-settings of multi meters have been designed to give you the proper reading right away. All we have to do is to make sure we have the right range, (although some of the digital meters are even self-adjusting and do all the work for us) multiply according to the indication on the range dial and we know the resistance of our component.

Some implements may give us a false reading with the best of care. For example, measure the resistance of a typical light bulb with an ohmmeter and then calculate the resistance from the wattage of the bulb. You'll find it is much less. That is because the light bulb's resistance increases considerably whenever it is lit. In principle, conductors increase their resistance as the temperature increases.

I hope this clears up your confusion.

QUESTION: What do we really pay for as we use electricity from the normal supply? Do we pay less when we, for example, use a transformer and use only 12V for something because it is only 12 V and not 115 or 220V? How is the amount of electricity measured in the meters?

ANSWER: Whenever we use electricity there are two values to be considered: Voltage (in Volts) and Current (in Amps or Amperes). The electricity companies are not interested how much you may transform up or down the voltage for whatever you want to use electricity for. They want to know how much, the AMOUNT you are consuming and for how long. How is the amount calculated?

You multiply the voltage and the current. That gives you the POWER that you use at that moment. We say it is so-and-so-many Watts. As one Watt is a very small amount we measure it (for costing purposes) in kW or kiloWatts. This is one thousand watts. Secondly they want to know how long you are using it. This is expressed in kWh, or kilo-Watt-Hours. The bill from the suppliers will tell you how many kWhs you have consumed and from that calculate the amount to be paid.

The ordinary electricity meter measures the Amount by creating a magnetic field. This depends on the voltage for a start. To avoid over- or under charging, any variations in voltage have to be taken into account. This magnetic field combined with that of the current consumed will turn a small aluminuim disk by induction. That is connected to a counter that can be read and the company will send you the bill for the amount of used electric power.

Peter.

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