# Notes on Electricity and Magnetism: Designed as a Companion to Silvanus P. Thompson's Elementary Lessons (Google eBook)

Macmillan & Company, 1884 - Electricity - 139 pages

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Page 100 - ... the angle between the plane of the coil and the direction of the lines, and as a field tends to become uniform would this advantage be gained.
Page 97 - A dynamo-electric machine is a machine for converting energy in the form of dynamical power into energy in the form of electric currents, by the operation of setting conductors (usually in the form of coils of copper wire) to rotate in a magnetic field.
Page 89 - Lenz, in 1834, summed up the matter by saying that in all cases of electromagnetic induction the induced currents have such a direction that their reaction tends to stop the motion which produces them.
Page 43 - Whether this force will be up or down will depend upon the direction of the current and the direction of the magnetic field. A rule which gives the direction of the force is as follows: If the index finger of the right hand is held pointing in the direction of the lines of force of the field and the middle finger (held at right angles with the index finger) points in the opposite direction to the current, then the conductor will tend to move in the direction of the outstretched thumb. If the direction...
Page 26 - intensity of the field " at any point is measured by the force with which it acts on a unit magnetic pole placed at that point. Hence, unit intensity of field is that intensity of field which acts on a unit pole with a force of one dyne. There is therefore a field of unit intensity at a point one centimetre distant from the pole of a magnet of unit strength. Suppose...
Page 26 - ... called a line of magnetic force. By drawing a sufficient number of such lines we may indicate the direction of the force in every part of the magnetic field ; but by drawing them according to rule, we may indicate the intensity of the force at any point as well as its direction. It has been shown J that if, in any part of their course, the number of lines passing through unit of area is proportional to the intensity there, the same proportion between the number of lines in unit of area and the...
Page 88 - ... or the other according to its polarity. This property enables the conventional direction to be determined by Ampere's rule, viz. : Suppose a man swimming in the wire with the current, and that he turns so as to face the needle, then the North-seeking pole of the needle will be deflected towards his left hand.
Page 26 - The unit magnetic pole may therefore be defined as that pole which repels a similar pole, at a distance of one centimetre, with a force of one dyne. Now the force exerted on a unit magnetic pole...
Page 32 - Magnetic Potential is essentially analogous to electrostatic potential. At any point, it is measured by the work done against the magnetic forces in moving a unit magnetic pole from an infinite distance to the given point. The difference of magnetic potential between two points is measured by the amount of work required to move a unit magnetic pole from one to the other. If this work is one erg, there is unit difference of potential between the two points.
Page 57 - In all our diagrams it is to be understood, that the planet, or satellite, moves through its orbit in the direction opposite to the motion of the hands of a watch.