Part 2 (1/2)

LETTER 4

THE BATTERIES IN YOUR RADIO SET

(This letter )

MY DEAR YOUNG MAN:

You will need several batteries when you come to set up your radio receiver but you won't use such cluravity cell which I described in my last letter Some of your batteries will be dry batteries of the size used in pocket flash lights

These are not really dry, for between the plates they are filled with a moist paste which is then sealed in ax to keep it fro Instead of zinc and copper these batteries use zinc and carbon No glass jar is needed, for the zinc is formed into a jar shape In this is placed the paste and in the center of the paste a rod or bar of carbon The paste doesn't contain sulphuric acid, but instead has in it a stuff called sal ammoniac; that is, ammonium chloride

The battery, however, acts very much like the one I described in my last letter Ions of zinc leave the zinc and wander into the moist paste

These ions are positive, just as in the case of the gravity battery The result is that the electrons which used to associate with a zinc ion to form a zinc atoative for it has more electrons than protons The zinc ions take the place of the positive ions which are already in the paste The positive ions which originally belonged with the paste, therefore, et so electrons away from the carbon leaves it with too many protons; that is, leaves it positive

In the little flash light batteries, therefore, you will always find that the round carbon rod, which sticks out of the center, is positive and the zinc casing is negative

The trouble with the battery like the one I used to make is that the zinc plate wastes away Every tireater part of an atoone Then when the two electrons which were left behind get a chance to start along a copper wire toward the positive plate of the battery there goes the rest of the atom After a while there is no more zinc plate It is easy to see what has happened

All the zinc has gone into solution or been ”eaten away” asbecause the zinc gets used up, but because the active stuff in the paste, the a else

There's another kind of battery which you will need to use with your radio set; that is the storage battery Storage batteries can be used over and over again if they are charged between ti tie current, that is, a big swift- stream of electrons You will need that when you wish to heat the filalish call our storage batteries by the name ”accumulators” I don't like that name at all, but I don't like our name for them nearly as well as I do the name ”reversible batteries” nobody uses this last nae battery is reversible, for it ork either way at an instant's notice

A storage battery is soon on a hill side It will run down hill but it can be pushed up again for another descent

You can use it to send a streaative plate to its positive plate Then if you connect these plates to soenerator, (that is, a dynao in the other direction When you have done so long enough the battery is charged again and ready to discharge

I ae battery but you ought to know a little about it if you are to own and run one with your radio set When it is all charged and ready to work, the negative plate is a lot of soft spongy lead held in place by a frame of harder lead

The positive plate is a lead frame with small squares which are filled with lead peroxide, as it is called This is a substance with en atoms Why the chemists call it lead peroxide instead of just lead oxide I'll tell you some other time, but not in these letters

Between the two plates is a wood separator to keep pieces of lead fro both plates You knoould happen if a piece of metal touched both plates There would be a short circuit, that is, a sort of a short cut across lots by which soet to the positive plate without going along the wires which ant them to travel That's why there are separators

The two plates are in a jar of sulphuric acid solution The sulphuric acid has molecules which split up in solution, as you reen ions and the ions which we called ”sulphate” In ravity battery the sulphate ions used to coax the zinc ions away into the solution In the storage battery on the other hand the sulphate ions can get to y When they do, they forht where the lead atoms are They don't really need whole lead atoms, because they have two more electrons than they deserve, so there are two extra electrons for every molecule of lead sulphate which is forative

The lead sulphate won't dissolve, so it stays there on the plate as a whitish coating Now see what thatas there was sulphuric acid in the water there was plenty of sulphate ions for them to associate with as often as they met; and they would et tied up with the lead of the plate there will be too en ions left in the solution Nohat are the hydrogen ions to do? They are going to get as far away fro but protons; and protons don't like to associate They only stayed around in the first place because there was always plenty of sulphate ions hoet away froo to the other plate of the battery, and there they will get some electrons, if they have to steal in their turn

I won't try to tell you all that happens at the other plate The hydrogen ions get the electrons which they need, but they get soen away from the plate and so form molecules of water You reen and one of oxygen Meanwhile, the lead atoen companions, cohborhood During the mix-up electrons are carried away from the plate and that leaves it positive

The result of all this is a little lead sulphate on each plate, a negative plate where the spongy lead was, and a positive plate where the lead peroxide was

Notice very carefully that I said ”a little lead sulphate on each plate” The sort of thing I have been describing doesn't go on very long If it did the battery would run down inside itself and then e caet out and crank

How long does it go on? Answer another question first So far we haven't connected any wire between the two plates of the battery, and so none of the electrons on the negative plate have any way of getting around to the positive plate where electrons are badly needed Every tiy lead of the negative plate there are two more electrons added to that plate You knoell electrons like each other Do they let the sulphate ions keep giving that plate more electrons? There is the other question; and the answer is that they do not Every electron that is added to that plate et near enough to do business at all That's why after a few extra electrons have accuy lead plate the actions which I was describing coain? They do just as soon as there is any reduction in the nuative plate trying to keep out of each other's way When we connect a wire between the plates we let so to the positive plate where they will be welcome And thecomes another sulphate ion in the solution and lands two more electrons on the plate