"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…

A rod with a slender wire coiled loosely around it.

Coil around rod

A rod with a slender wire coiled loosely around it.

"Construction of condenser for an induction coil." — Hawkins, 1917

Condenser

"Construction of condenser for an induction coil." — Hawkins, 1917

"The electric screen. A screen of wire gauze surrounding a delicate electrical instrument will protect it from external electrostatic induction." -Hawkins, 1917

Electric Screen

"The electric screen. A screen of wire gauze surrounding a delicate electrical instrument will protect…

"The electrophorus and meethod of using. Charge B; place A in contact with B, and touch A (left illustration). The disc is now charged by induction and will yield a spark when touched by the hand (right illustration)." -Hawkins, 1917

Electrophorus

"The electrophorus and meethod of using. Charge B; place A in contact with B, and touch A (left illustration).…

Alessandro Volta's design of the electrophorus. "An instrument for obtaining statical electricity by means of induction." -Whitney, 1911

Electrophorus

Alessandro Volta's design of the electrophorus. "An instrument for obtaining statical electricity by…

"In the gold-leaf electroscope (invented by Bennet in 1787), two light strips of gold-leaf hang from the lower end of a metal rod, which passes vertically through an opening in the top of a glass bottle and expands above into a plate. If a piece of rubbed sealing-wax or other electrified body be brought near the plate, the gold leaves will repel each other and diverge ... A cylinder of wire gauze placed just inside the glass case, improves the action of the instrument." -Hazeltine, 1894

Gold Leaf Electroscope

"In the gold-leaf electroscope (invented by Bennet in 1787), two light strips of gold-leaf hang from…

Device for electrostatic induction.

Electrostatic Induction

Device for electrostatic induction.

"The induction coil is...often called the Rhumkorff coil. Receiving a large current of small electromotive force, it delievers a small current at a high pressure, sometimes hundreds of thousands of volts, i.e., it is a 'step up' transformer." -Avery 1895

Induction Coil

"The induction coil is...often called the Rhumkorff coil. Receiving a large current of small electromotive…

"The induction coil is...often called the Rhumkorff coil. Receiving a large current of small electromotive force, it delievers a small current at a high pressure, sometimes hundreds of thousands of volts, i.e., it is a 'step up' transformer." -Avery 1895

Induction Coil

"The induction coil is...often called the Rhumkorff coil. Receiving a large current of small electromotive…

Induction motor.

Induction Motor

Induction motor.

"Experiment to illustrate electrostatic induction. The leaves will diverge, ever though the charged ebonite rod does not approach to within a foot of the electroscope." -Hawkins, 1917

Electrostatic Induction

"Experiment to illustrate electrostatic induction. The leaves will diverge, ever though the charged…

"Bring a metallic sphere postively charged near an insulated cylindrical conductor with hemispherical ends and provided with pith-ball and lined thread electroscopes as shown. The divergence of the pith-balls shown electrification at the ends but not at the middle of the conductor." -Avery 1895

Electrostatic Induction

"Bring a metallic sphere postively charged near an insulated cylindrical conductor with hemispherical…

"Suspend two egg-shell conductors as shown. Be sure that the shells are in contact. Bring an electrified glass rod near one of them, and slide one of the loops along the supporting rod until the shells are about 10 cm. apart. Hold the electrified rod between the shells. It will attract one and repel the other, showing that thye are oppositely electrified." -Avery 1895

Electrostatic Induction

"Suspend two egg-shell conductors as shown. Be sure that the shells are in contact. Bring an electrified…

"Lines of force of a charged sphere and a conductor under induction. The negative electrification on the end a of the cylinder indicates that an equal number of lines set out from that end." -Hawkins, 1917

Lines of Force under Induction

"Lines of force of a charged sphere and a conductor under induction. The negative electrification on…

"Machine used to generate electricity by induction using transformed kinetic energy from the crank." -Avery 1895

Induction Machine

"Machine used to generate electricity by induction using transformed kinetic energy from the crank."…

The first inauguration of William McKinley, the 25th President of the United States, on March 4, 1897.

First inauguration of William McKinley

The first inauguration of William McKinley, the 25th President of the United States, on March 4, 1897.

"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." — Hawkins, 1917

Magnetic spool

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

"Diagram of a vibrator coil. The parts are as follows: A, contact screw; B, battery; C, core; D, vibrator terminal; G, condenser; P, primary winding; S, secondary winding; W, switch; Y, vibrator." -Hawkins, 1917

Vibrator Coil

"Diagram of a vibrator coil. The parts are as follows: A, contact screw; B, battery; C, core; D, vibrator…