"Magnetic hysteresis in armature core. Unlike poles are induced in the core opposte the poles of the field magnet. Since on account of the rotation of the core the induced poles are reversed a thousand or more times a minute, considerable energy is required to change the positions of the molecules f the iron for each reversal, resulting in the generation of heat at the expense of a portion of the energy required to drive the armature." -Hawkins, 1917

Magnetic Hysteresis in Armature Core

"Magnetic hysteresis in armature core. Unlike poles are induced in the core opposte the poles of the…

"Distribution of magnetic lines through a ring armature. Since the lines follow the metal of the ring instead of penetrating the interior no electromotive force is induced in that portion of the winking lying on the interior surface of the ring. There is, therefore, a large amount of dead wire or wire that is ineffective in inducing electromotive force; that is the chief objective to the ring type of armature." -Hawkins, 1917

Distribution of Magnetic Lines, Ring Armature

"Distribution of magnetic lines through a ring armature. Since the lines follow the metal of the ring…

"The horizontal angular distance between two meridians. <em>Magnetic A.</em> the horizontal angular distance of the magnetic from the geographical meridian. <em>A. compass</em>; a variety of ship's compass." &mdash; Williams, 1889

Azimuth

"The horizontal angular distance between two meridians. Magnetic A. the horizontal angular…

A magnetic compass.

Compass

A magnetic compass.

"A magnet which owes its magnetic properties to the inductive action of an electric current." -Whitney, 1911

Electromagnet

"A magnet which owes its magnetic properties to the inductive action of an electric current." -Whitney,…

"Pith ball pendulum or electroscope; the figures illustrate also electrical attraction and repulsion." -Hawkins, 1917

Electroscope Attraction and Repulsion

"Pith ball pendulum or electroscope; the figures illustrate also electrical attraction and repulsion."…

"Around a vertical conductor carrying a heavy current, place a peice of paper and sprinkle iron filling on the paper. Notice that the iron particles arrange themselves in distinct circular whirls around the wire, as shown." -Avery 1895

Magnetic Field Due to Current

"Around a vertical conductor carrying a heavy current, place a peice of paper and sprinkle iron filling…

"If the conducting wire is bent into the form shown, the lines of force will pas around the wire from one face of the loop to the other, and in the direction indicated by the 'rule of thumb' just given." -Avery 1895

Magnetic Field Around a Current Carrying Wire

"If the conducting wire is bent into the form shown, the lines of force will pas around the wire from…

"The magnetic poles of the earth do notc oincide with its geographical poles and, condequently, in some places, the magnetic needle does not point ot the geographical north. The angle that the axis of a compass-bneedle makes with the geographical meridian at any place is called the declination or variation of the needle at that place...Lines drawn through places on the earth where the declination is the sam are called isogonic lines, as shown." -Avery 1895

Isogonic Lines of Earth

"The magnetic poles of the earth do notc oincide with its geographical poles and, condequently, in some…

"Kew Instruments arranged in the relative positions recommended by Lloyd so as magnetically to interfere with one another as little as possible. We are supposed to be viewing the whole from the south. No. 1 to the right is the declination instrument, No. 2 that for the horizontal force, and No. 3 in the distance behind the central pillar (No. 4) the vertical force magnetometer." &mdash;The Encyclopedia Britannica, 1903

Kew Instruments

"Kew Instruments arranged in the relative positions recommended by Lloyd so as magnetically to interfere…

A type of magnet whose magnetic field is produced by the flow of electric current. The magnetic field disappears when the current ceases.

Electro Magnet

A type of magnet whose magnetic field is produced by the flow of electric current. The magnetic field…

An illustration of a horseshoe shaped magnet.

Horseshoe Magnet

An illustration of a horseshoe shaped magnet.

An illustration of a rectangle shaped steel magnet with "consequent poles at a and b." -Century, 1889

Rectangle Shaped Steel Magnet

An illustration of a rectangle shaped steel magnet with "consequent poles at a and b." -Century, 1889

"The region about a magnet in which its magnetic forces can be detected is called the magnetic field. This can be graphically represented by placing a piece of cardboard over the magnet and sprinkling ironn fillings on the paper, gently tapping at the same time." -Hawkins, 1917

Magnetic Field

"The region about a magnet in which its magnetic forces can be detected is called the magnetic field.…

"Tracing lines of force with a suspended magnet." -Hawkins, 1917

Tracing magnetic field lines

"Tracing lines of force with a suspended magnet." -Hawkins, 1917

Figure showing magnetic lines of force from a magnet, as well as both north and south poles.

Magnetic Field

Figure showing magnetic lines of force from a magnet, as well as both north and south poles.

"Oersted's experiements are illustrated...which shows, at A, B, C and D, the four different positions which a balanced magnetic needle tends to assume when placed parallel to a wire through wich an electric current is flowing in the different directions indicated by the arrows..." -Atkinson 1903

Deflection of te Magnetic Needle by the Electric Current

"Oersted's experiements are illustrated...which shows, at A, B, C and D, the four different positions…

"Magnetic field of a solenoid. This is best observed by cutting a piece of cardboard and fitting it around the solenoid, as shown." -Hawkins, 1917

Magnetic field, solenoid

"Magnetic field of a solenoid. This is best observed by cutting a piece of cardboard and fitting it…

"A bar of steel which is a magnet, suspended in such a way that it can freely turn to the north or south." &mdash;Wells, 1857

Magnetic Needle

"A bar of steel which is a magnet, suspended in such a way that it can freely turn to the north or south."…

"Morse magnetic telegraph will be understood by reference to the accompanying diagram, which represents the construction and arrangement of this form of telegraph. F and E are pieces of soft iron surrounded by coils of wire, which are connected at a and b with wires proceeding from a galvanic battery. When a current is transmitted from a battery located one, two, or three hundred miles, as the case may be, it passes along the wires and into the coils surrounding the pieces of soft iron F and E, thereby converting them into magnets. Above these pieces of soft iron is a metallic bar or lever, A, supported on its center, and haing at one end the arm D, and at the other a small steel point, o. A ribbon of paper, p h, rolled on the cylinder B, is drawn slowly and steadily off by a train of clock-work, K, moved by the action of the weight P on the cord C. This clock-work gives motion to two metal rollers, G and H, between which the ribbon of paper passes, and which, turnin in opposite directions, draw the paper from the cylinder B. The roller H has a groove arond its circumference (not represented in the engraving) above which the paper passes. The steel point, r, or the lever, A, is also directly opposite this groove. The spring r prevents the point from resting upon the paper when the telegraph is not in operation." &mdash;Wells, 1857

Magnetic Telegraph

"Morse magnetic telegraph will be understood by reference to the accompanying diagram, which represents…

"Experiment illustrating the molecular theory of magnetism. Coarse steel filings are placed inside a small glass tube and the contents magnetized. It will be found that filing which at first had no definite arrangement will rearrange themselves under the influence of magnetic force, and assume symmetrical position, each one lying in line with, or parallel to its neighbor, as shown in the lower figure." -Hawkins, 1917

Magnetism

"Experiment illustrating the molecular theory of magnetism. Coarse steel filings are placed inside a…

"The machine itself is sufficiently simple, and will be comprehended at once, by those who have made electro-magnetic experiments, by the annexed diagram and description. The temporary magnet a, enveloped with its insulated copper wire, is fastened to the wooden frame b, g, by means of cords or otherwise. The frame also supports the standard h, which sustains the revolving drum f, on which the paper to receive the emblematical alphabet is fixed, m being the edge of the paper. To the arm g, is appended the lever c, of wood, which has a slight vertical motion, in one direction by the steel spring d, and in the other, by the armature of soft iron e." &mdash;Comstock, 1850

Morses Telegraph

"The machine itself is sufficiently simple, and will be comprehended at once, by those who have made…

"Right hand rule to determine the direction of magnetic field around a conductor carrying a current. The thumb of the right hand is placed along the conductor, pointing in the direction in which the current is flowing, then...the finger tips will point in the direction of the magnetic whirls." -Hawkins, 1917

Right Hang Rule

"Right hand rule to determine the direction of magnetic field around a conductor carrying a current.…

Device for separating, by means of an electromagnet, magnetic particles in a slurry from the remainder of the particles in the mixture. Used in the recovery of medium in heavy-media separation.

Magnetic Separator

Device for separating, by means of an electromagnet, magnetic particles in a slurry from the remainder…

"Place a strip of shet iron in the solenoid, as shown...Hotice that most of the lines of force are gathered into the iron and issue from its ends. Notice that the lines curve outward and tend to return, forming closed loops or complete magnetic circuits. Change the iron from the inside of the solenoid to the outside, and repeat...Notice that the iron again gathers in the lines of force as if it offered an easier path for them." -Avery 1895

Solenoid with Iron Bar

"Place a strip of shet iron in the solenoid, as shown...Hotice that most of the lines of force are gathered…

"Method of winding magnet spool so that the two ends of the coil will come to the outside. This method has also been used for induction coils, where it is desirable to keep the ends of the wire away from the core and primary coil." &mdash; Hawkins, 1917

Magnetic spool

"Method of winding magnet spool so that the two ends of the coil will come to the outside. This method…

A man operating an electro-magnetic telegraph.

Telegraph

A man operating an electro-magnetic telegraph.