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acid alternating current ammeter amount ampere-hours amperes apparatus armature core battery brass brushes candle carbon cause cell coil commutator conductor connected considerable convolutions copper current flowing current strength curve Daniell cell deflection developed diameter difference of potential direction distance dynamo eddy currents effect electrical electro-magnetic electro-motive force employed equal external circuit external resistance field field-magnet fixed galvanometer heat horizontal inch increase instrument insulated lamp length lines of force machine magnetic magnetising maximum measured mercury metal method motor needle number of lines obtained ohms pair parallel passing piece placed plate platinum pole pole-pieces portion position potential difference practical proportional reduced result revolutions per minute right angles ring rotation round screw secondary self-induction shaft shown in fig soft iron solenoid speed spiral strip sulphate sulphuric acid surface tangent galvanometer temperature terminals tion tube turns varies vertical voltmeter volts wire wound zinc
Page 567 - How would you prove that the illumination on any surface is inversely as the square of its distance from the source of light ? 6.
Page 41 - The unit of work is called the ' erg,' and is that work done when a force of one dyne is overcome through a distance of one centimetre ; the energy expended is in every case equal to the work done, therefore the erg is also the unit of energy. We have seen that the practical unit of work, or expenditure of energy, is the joule : and one joule is equal to ten million ergs. Consequently, the practical unit of power, or rate of doing work, called the watt, is equivalent to ten million ergs per second.
Page 208 - ... and r is the radius of the circle. If, therefore, the diameter of the outside layer is actually twice that of the inside, the length of the wire in each of the larger turns, and consequently in the whole layer, will be exactly doubled, and its resistance doubled also ; and the intermediate layers will vary proportionately.
Page 231 - As the induced EMF is proportional to the rate at which the lines of force are cut, it is only necessary, in order to decide this question, to ascertain whether the rate of cutting is, under the circumstances, also uniform. A little reflection will show that just when the rectangle begins to move from its position in fig.
Page 536 - To explain the construction of the common barometer, and to shew that the mercury is sustained in it by the pressure of the air on the surface of the mercury in the basin.
Page 239 - ... eddy' or Foucault currents. Their initial direction is at right angles to the lines of force of the magnetic field, and also at right angles to the direction in which the mass moves ; therefore, in the shuttle armature, they travel lengthways along the iron core, completing their circuit in a more or less circular path in the iron (whence they...
Page 233 - FIG. 125. number of linos of force by moving through 30° when its plane is nearly parallel to the direction of the lines, than it does by moving through an equal angle while it is nearly perpendicular to them. But as the speed of rotation is uniform, it takes precisely the same time to pass through these equal angles, therefore the rate of cutting, and consequently the EMF, must be much greater in the former than in the latter case. In fact, the rate at any moment is proportional to the sine of...
Page 495 - ... same intensity. For the sake of those of our readers who are not acquainted with the character of a beam of light, a few words on the subject may not be out of place. Pure white light is in reality composed of rays of seven different colours superposed upon one another, or blended together.
Page 38 - The quantity of work performed in raising a mass of one pound through a difference of level of one foot against the force of gravity, is generally taken as the unit of mechanical energy and is known as the foot-pound. The work done in raising any mass through any height, is found by simply multiplying together the number of pounds in that mass by the number of feet through which it is lifted. Somewhat similarly we can take as the practical unit of electrical energy, the amount expended in transferring...