Absolute Measurements in Electricity and MagnetismMacmillan and Company, 1884 - 207 стор. |
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Загальні терміни та фрази
ampere arrangement axis battery blue pole c.g.s. units capacity cell centimetres centre change-ratio coil conductor connected convenient copper cross-section current flowing current strength deflection denote density determined difference of potentials dimensional formula distance dynamo E₁ earth's electric force electrical efficiency Electricity and Magnetism electromagnetic units electromotive force electrostatic equal equation equivalent Hence horizontal induction instrument insulated intensity joules lines of force magnetic field magnetic force magnetic matter magnetic moment magnetic pole magnetometer mean measured method motor multiplied needle number of lines number of turns numeric Ohm's law P₁ pendulum placed plane plate pole faces positive electricity potential galvanometer practical unit produced projecting arm quadrants quantity of electricity r₁ R₂ ratio rectangle right angles round self-induction side slider solenoid suppose surface suspended terminals thread unit of length V₁ V₂ velocity vertical volts Wheatstone's Bridge wire zero
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Сторінка 73 - ... the circuit by its resistance is equal to the sum of the electromotive forces in the circuit. This follows at once by an application of Ohm's law to each part of the circuit, exactly as in the investigation in p.
Сторінка 43 - A current of this strength — that is, the current flowing in a wire of resistance one ohm, between the two ends of which a difference of potentials of one volt is maintained, — has been adopted as the practical unit of current and called one ampere. Hence it is to be remembered one ampere is one-tenth of one cgs unit of current. The amount of electricity conveyed in one second by a current of one ampere is called one coulomb. This unit although not quite so frequently required as the others,...
Сторінка 44 - Therefore a conductor in a magnetic field, and carrying a unit current which flows at right angles to the lines of force, is acted on by a force tending to move it in a direction at right angles to its length, and the magnitude of this force for unit length of conductor, and unit field, is by the definition of unit current equal to unity. Applying this to our slider in which we may suppose a current of strength...
Сторінка 137 - Instead of a single wire cutting the lines of force, a coil of proper dimensions (for many purposes conveniently of rectangular shape), the mean area of which is exactly known, may be suspended in the field with its plane parallel to the lines of force, and turned quickly round through a measured angle of convenient amount not exceeding 90°; or it may be suspended with its plane at right angles to the lines of force and turned through an angle of 180°. If n be the number of turns, A their mean...
Сторінка 25 - ... circle, we may suppose that each pole of the magnet is at the same distance from all the elements of the wire. A current flowing in the wire acts, by Ampere's theory, with a force on one pole of the needle towards one side of the plane of the circle, and on the other pole with an equal force toward the other side of that plane. The needle is thus acted on by a couple tending to turn it round, and it is deflected from its position of equilibrium until this couple is balanced by the return couple...
Сторінка 37 - A and £ of a. homogeneous wire, in which a uniform current of electricity is kept flowing by any means, there exists a difference of potentials, and that if the wire be of uniform section throughout, the difference of potentials is in direct proportion to the length of wire between the cross-sections.
Сторінка 15 - ... centres of gravity" of magnetic polarity, should be determined by experiment : and allowances should be made for the magnitude of the arc of vibration ; the torsional rigidity of the suspension fibre of cocoon silk of the magnetometer in the deflection experiments, and of the suspension fibre of the magnet in the oscillation experiments ; the frictional resistance of the air to the motion of the magnet ; the virtual increase of inertia of the magnet due to motion of the air in the chamber ; and...
Сторінка 39 - Hence if the intensity of the field we have imagined be i cgs unit, the distance between the rails i cm., and the velocity of the slider i cm. per second, the difference of potentials produced will be i cgs unit. This difference of potentials is so small as to be inconvenient for use as a practical unit, and instead of it the difference of potentials which would be produced if, everything else remaining the same, the slider had a velocity of 100,000,000 cms. per second, is taken as the practical...
Сторінка 35 - ... these two radial lines when its point is at the corresponding division on the circle the adjustment is correct. When taking readings the observer places his eye so as to see the index just cover its image in the mirror bottom of the box, and reads off the number of degrees and fraction of a degree, indicated on the scale by the position of the index. Error from parallax is thus avoided. A mirror with attached magnets may be used, as in the magnetometer, instead of the needle and index. When this...
Сторінка 43 - The work done by a force is equal to the product of the force and the distance through which the point of application is moved in the direction of the force...