Part 4 (1/2)

[Illustration: _Fig 40_ CROSS SECTION OF DETECTOR]

HOW TO PLACE THE DETECTOR--If the detector is placed north and south, as shown by the two net bar will point north and south, being affected by the earth's h the coil (B), the ht or to the left, so that the pointer (O) will then show the direction in which the current is flowing through the wire (R) which you are testing

The next step of importance is to _th or intensity, as well as the flow or quantity

DIFFERENT WAYS OF MEASURING A CURRENT--There are several ways to measure the properties of a current, which may be defined as follows:

1 THE SULPHURIC ACID VOLTAMETER--By means of an electrolytic action, whereby the current decomposes an acidulated solution--that is, water which has in it a senerated by the current

2 THE COPPER VOLTAMETER--By electro-cheh plates immersed in a solution of copper sulphate

3 THE GALVANOSCOPE--By having a coil of insulated wire, with awhat is called a galvanoscope

4 ELECTRO-MAGNETIC METHOD--By using a pair of h the coils, and thenthe pull on the ar an electric fan, and noting the revolutions produced by the current

6 THE CALORIMETER--By using a coil of bare wire, i the temperature by41_ ACID VOLTAMETER]

[Illustration: _Fig 42_ COPPER VOLTAMETER]

7 THE LIGHT METHOD--Lastly, by htness, a greater or less current

THE PREFERRED METHODS--It has been found that the first and second ister current strength, and these e--that the chemical effect produced is not dependent upon the size or shape of the apparatus or the plates used

HOW TO MAKE A SULPHURIC ACID VOLTAMETER--In Fig 41 is shown a simple form of sulphuric acid voltahtly closed by a cover (B) Within is a pair of platinuh the cover The cover has a vertical glass tube (E) through it, which extends down to the botto a weak solution of sulphuric acid When a current passes through the wires (D), the solution is partially decoas, which passes up into the vacant space (F) above the liquid, and, as it cannot escape, it presses the liquid doardly, and causes the latter to floardly into the tube (E) It is then an easy matter, after the current is on for a certain tiht of the liquid in the tube

HOW TO MAKE A COPPER VOLTAMETER--The second, or copper voltalass jar (A) contains a solution of copper sulphate, known in commerce as blue vitriol A pair of copper plates (B, B') are placed in this solution, each being provided with a connecting wire (C) When a current passes through the wires (C), one copper plate (B) is eaten away and deposited on the other plate (B') It is then an easy ht B' has gained, or how th of, say, two separate currents, one should have each current pass through the voltath of time as the other, so as to obtain comparative results

It is not necessary, in the first and second methods, to consider the shapes, the sizes of the plates or the distances between theiven time, will be the same, and in the second method the amount deposited or eaten aill be the same under all conditions

DISADVANTAGES OF THE GALVANOSCOPE--With the third et a positively correct reading instru each part, in every detail, and great careIt is necessary also to be very careful in selecting the sizes of wire used and in the number of turns made in the coils

This is equally true of the fourth netic pull is dependent upon the size of wire from which the coils are made and the number of turns of wire

OBJECTIONS TO THE CALORIMETER--The calorialvanoscope and electro-net do not respond equally to all currents, and this is also true, even to a greater extent, with the calorimeter

CHAPTER VI

VOLTS, AMPERES, OHMS AND WATTS

UNDERSTANDING TERMS--Weof some of the terms so frequently used in connection with electricity If you intended to sell or oods of any kind, it would be essential to kno allon, or in a bushel, or how ht to know just what the quantity term _bushel_ or the measurement _yard_ means

INTENSITY AND QUANtitY--Electricity, while it has no weight, is capable of being ht ht is of less intensity than another and both of them receive their i which interferes with that light which shows the least brilliancy Electricity can also be interfered with, and this interference is called _resistance_

VOLTAGE--Water reater or less force, or velocity, through a pipe, the degree of saht of the water which supplies the pipe So with electricity It reater or less force under one condition than another