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"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.…

"Right hand rule for polarity of a solenoid: If the solenoid be grasped in the right hand, so that the fingers point in the direction in which the current is flowing in the wires, the thumb extended will point in the direction of the north pole [of the solenoid]." Hawkins, 1917

Right Hand Rule, Solenoid

"Right hand rule for polarity of a solenoid: If the solenoid be grasped in the right hand, so that the…

"Fleming's rule for direction of induced current. Extend the thumb, forefinger and middle finger of the right hand [as shown]. Place the hand [so that] the thumb will point in the direction in which the conductor moves, the forefinger in the direction of the lines of force (N to S), then will the middle finger point in the direction in which the induced current flows." -Hawkins, 1917

Right Hand Rule of Induced Current

"Fleming's rule for direction of induced current. Extend the thumb, forefinger and middle finger of…

"The palm rule for direction of induced current: If the palm of the right hand be held against the direction of the lines of force, the thumb in the direction of the motion, then the fingers will point in the direction of the induced current." -Hawkins, 1917

Right Hand Rule, Palm

"The palm rule for direction of induced current: If the palm of the right hand be held against the direction…

"The electric telegraph in its simplest form, consists of an electric circuit connecting he points between which telegraphic intercourse is established, a battery at each point, connected wih this circuit, and two instruments, one for transmitting and the other for receiving electric impluses by with arbitrary sign representing written language are produced." -Atkinson 1903

Simple Telegraph

"The electric telegraph in its simplest form, consists of an electric circuit connecting he points between…

"Suppose a cannon ball, tied with a string to the centre of a slab of smooth marble, and suppose an attempt be made to push this ball with the hand in the direction of b; it is obvious that the string would prevent its going to that point; but would keep it in thei circle. n this case, the string is the centripedal force." -Comstock 1850

Centrifugal Force

"Suppose a cannon ball, tied with a string to the centre of a slab of smooth marble, and suppose an…

"The center of gravity, in any body or system of bodies is that point upon which the body, or system of bodies, acted upn only by gravity will balance itself in all positions." -Comstock 1850

Center of Gravity

"The center of gravity, in any body or system of bodies is that point upon which the body, or system…

"In a body of equal thickness, as a board, or a slab of marble, but otherwise of an irregular shape, the centre of gravity may be found by suspending it, first from one point, and then from another, and marking, by means of a plumb line, the perpendicular ranges from the point of suspension. the centre of gravity will be the point where these two lines cross each other." -Comstock 1850

Center of Gravity

"In a body of equal thickness, as a board, or a slab of marble, but otherwise of an irregular shape,…

"If the plane is inclined downwards, the ball is instantly thrown into motion, because the centre of gravity then falls forward of that motion, or the point on which the ball rests." -Comstock 1850

Center of Gravity of a Ball Rolling on an Incline

"If the plane is inclined downwards, the ball is instantly thrown into motion, because the centre of…

"Where five blocks are placed in this position, the point of gravity is near the centre of the thrd block, and is within the base as shown by the plumb line. But on adding another block, the gravitation point falls beyond the base, and the whole will now fall by its own weight." -Comstock 1850

Center of Gravity of Standing Blocks

"Where five blocks are placed in this position, the point of gravity is near the centre of the thrd…

"But, suppose the same bar or iron, whose inertia was overcome by raising the centre, to have balls of different weights attached to its ends; then the centre of inertia would no longer remain in the middle of the bar, but would be changed to the point A..." -Comstock 1850

Center of Inertia

"But, suppose the same bar or iron, whose inertia was overcome by raising the centre, to have balls…

"In the single moveable pulley, the same rope passes from the fixed point, A, to the power, P. It is evident here, that the weight, W, ten pounds, five pounds will be supported by one string, and five by the other. The power will then support twice its own weight." -Comstock 1850

Single Movable Pulley

"In the single moveable pulley, the same rope passes from the fixed point, A, to the power, P. It is…

"In a circle, sound is reflected from every plane surface placed around it, and hence, if the sound is emitted from the centre of a circle, this centre will be the point at which the echo will be most distinct." -Comstock 1850

Sound Reflection in a Circle

"In a circle, sound is reflected from every plane surface placed around it, and hence, if the sound…

"Suppose the rod a, to be set with one half of its length below the surface of the water and the other half above it. The eye being placed in an oblique direction will see the lower end apparently at the point o, while the real termination of the rod would be at n; the refraction will therefore make the rod appear shorter by the distance from o to n, or one-fourth shorter than the part below the water really is." -Comstock 1850

Refraction, water

"Suppose the rod a, to be set with one half of its length below the surface of the water and the other…

"Rays of light are said to diverge, when they proceed from the same point, and constantly recede from each other, as from the same point a. Rays of light are said to converge, when they approach each other in such a drection as finaly to meet at a point, as at b." -Comstock 1850

Rays of Light

"Rays of light are said to diverge, when they proceed from the same point, and constantly recede from…

"If the object a be placed obliquely before the convex mirror, then the converging rays from its two extremities falling obliquely on its surface, would they prolonged through the mirror, meet at the point c, behind it. But instead of being thus continued, they are thrown back by the mirror in less convergent lines, which meet the eye at e, it being, as we have seen, one of the properties of this mirror, to reflect converging rays less convergent than before." -Comstock 1850

Curved Image

"If the object a be placed obliquely before the convex mirror, then the converging rays from its two…

"Let us suppose that a, is a luminous point, from which a pencil of diverging rays falls upon a convex mirror. These rays, as already demonstrated, will be reflected more divergent, and consequently will meet the eye at e, in a wider state of dispersion that they fell upon the mirror at o." -Comstock 1850

Convex Mirror

"Let us suppose that a, is a luminous point, from which a pencil of diverging rays falls upon a convex…

"The focus of a concave mirror is the point where the rays are brought together by reflection." -Comstock 1850

Focus of a Concave Mirror

"The focus of a concave mirror is the point where the rays are brought together by reflection." -Comstock…

"...be made obvious...where the diverging rays 1, 2, 3, 4 form a focus at the point o, whereas, had they been parallel, their focus would have been at a." -Comstock 1850

Divergent Rays in a Concave Mirror

"...be made obvious...where the diverging rays 1, 2, 3, 4 form a focus at the point o, whereas, had…

"These pencils of rays not only flow from the points designated in the figure, but in the same manner from every other point on the surface of a visible object." -Comstock 1850

Pencils of Rays

"These pencils of rays not only flow from the points designated in the figure, but in the same manner…

"Suppose a, to be a distinct object, from which pencils of rays flow from every point toward the object lens b. The image of a, in consequence of the refraction of the rays by the object lens, is inverted at c, which is the focus of the eyeglass d, and through which the image is then seen, still inverted." -Comstock 1850

Refracting Telescope

"Suppose a, to be a distinct object, from which pencils of rays flow from every point toward the object…

"One of the simplest instruments of this kind consists of a metallic needle, terminated at each end by a light pith-ball, which is covered with gold leaf, and supported horizontally at its centre by a fine point.." -Comstock 1850

Electroscope

"One of the simplest instruments of this kind consists of a metallic needle, terminated at each end…

"Thus, if we suppose the conducting wire be placed in a vertical situation, as shown, and p, n, the current of positive electricity to be descending through it, from p to n, and if throught the point c in the wire in the plane NN be taken, perpendicular to p, n, that is in the present case a horiczontal plane, then if any number of circles be described in that plane, having c for thier common centre, the action of the current on the wire on upon the north pole of the magnet, will be to move it in a direction corresponding to the motion of the hands of a watch, having the dial towards the positive pole of the battery." -Comstock 1850

Circular Motion of the [Electric] Fluid

"Thus, if we suppose the conducting wire be placed in a vertical situation, as shown, and p, n, the…

"The angle, ABD, included between the direction of the moving body before it strikes the reflecting surface, and a perpendicular to that surface drawn from the point of contact, is called the angle of incidence. The angle between the perpendicular and the direction of the moving body after striking is called the angle of reflection." -Avery 1895

Law of Reflected Motion

"The angle, ABD, included between the direction of the moving body before it strikes the reflecting…

"A body's center of mass is the point about which all matter composing the body may be balanced. It is also called the center of inertia. In some cases, this is also the center of gravity." -Avery 1895

Center of Mass

"A body's center of mass is the point about which all matter composing the body may be balanced. It…

"Let any irregularly shpaed body, as a stone or chair, be suspended so as to move freely. Drop a plumb line from the point of the suspendsion, and make it fast or mark its direction. The center of mass will lie in this line. From a second point, not in the line already determined, suspend the body; let it fall a plumb line as before. The center of mass will lie in this line also. But to lie in both lines, it must lie at their intersection." -Avery 1895

Finding the Center of Mass

"Let any irregularly shpaed body, as a stone or chair, be suspended so as to move freely. Drop a plumb…

"When the pendulum is drawn from its vertical position, the force of gravity, MG, is resolved into two components, one of which, MC, produces pressure at the point of support, while the other, MH, acts at right angles to it, producing motion toward N." -Avery 1895

Motion of a Pendulum

"When the pendulum is drawn from its vertical position, the force of gravity, MG, is resolved into two…

"The Nicholson hydrometer of constant volume is a hollow cylinder carrying at its lower end a basket, d, heavy enough to keep the apparatus upright in water. At the top of the cylinder is a vertical rod carrying a pan, a, for holding weights, etc. The whole apparatus must be lighter than water, so that a certain weight (W) must be put into the pan to sink the apparatus to a fixed point marked on the rod (as c). The given body, which must weigh less than W, is placed in the pan, and enought weights (w) added to sink the point c, to the water line It is evident that the weight of the given body is W-w." -Avery 1895

Nicholson Hydrometer

"The Nicholson hydrometer of constant volume is a hollow cylinder carrying at its lower end a basket,…

"The vertical distance form the level of the upper liquid to the highest point of the tube (ab) is the length of one arm; the vertical distance from the highest point of the tube to the lower end of the tube, or to the level of the liquid into which it dips (cd), is the length of the other arm. The second of these must exceed the first." -Avery 1895

Siphon

"The vertical distance form the level of the upper liquid to the highest point of the tube (ab) is the…

"Hold a lamp reflector or other large concave mirror directly facing the sun, so as to bring the rays of light to a focus...At some point, W, between F and C, the center of curvature of the reflector, hang a loud-ticking watch, and hunt for the point, X, at which the ear can most distinctly hear the ticking. Moving the reflector will render the sound inaudible." -Avery 1895

Reflection of Sound Using a Reflector

"Hold a lamp reflector or other large concave mirror directly facing the sun, so as to bring the rays…

"Lightly touch the wire at its middle point with the tip of the finger or the beard of a quill; the wire will vibrate in halves." -Avery 1895

Sound Wave

"Lightly touch the wire at its middle point with the tip of the finger or the beard of a quill; the…

"Start a trough from A. At the moment of its reflection as a crest a B, start a crest at A as shown. The two crests will meet near the middle of the rope. The crest at the point and moment of meeting results from two forces acting in the same direction; their resultatnt is greater than either of the components." -Avery 1895

Constructive Interference

"Start a trough from A. At the moment of its reflection as a crest a B, start a crest at A as shown.…

"Using the rope...start a crest at A. At the moment of its reflection at B as a trough, start a second crest at A. The trough and crest will meet near the middle of the rope. the rope particles at this point, being thus simultaneously acted upon by opposite forces, will remain at rest or nearly so." -Avery 1895

Destructive Interference

"Using the rope...start a crest at A. At the moment of its reflection at B as a trough, start a second…

"Support, as shown, a glass or brass plate, square or round, and strew it evenly with fine sand. Place the finger at any point of the edge of the plate, so as to form a node there, and draw a violin bow at a point properly chosen. The sand immediately begins to dance on the plate and arrange itself along nodal lines. By changing the nodal points and bowing properly, other sand-figures may be produced, one of which is shown." -Avery 1895

Vibrating Plates

"Support, as shown, a glass or brass plate, square or round, and strew it evenly with fine sand. Place…

"If an object is placed before a plane mirror, a virtual image appears behind the mirror. Each point of this image seems to be as far behind the mirror as the corresponding point of the object is in front of the mirror. Hence, images seen in still, clear, water are inverted." -Avery 1895

Plane Mirror

"If an object is placed before a plane mirror, a virtual image appears behind the mirror. Each point…

"When the rays diverge from a point beyond the center of curvature, as B, the focus falls on the same axis, at a distrance from the mirror greater than that of the principal focus, and less than that of the center of curvature." -Avery 1895

Rays Diverging from Beyond the Center of Curvature on a Concave Mirror

"When the rays diverge from a point beyond the center of curvature, as B, the focus falls on the same…

"When the rays diverge form a point at a distance from the mirror less than that of the principal focus, the reflected rays diverge as if from a point back of the mirrir. This point, b, is a virtual focus." -Avery 1895

Rays Diverging from Beyond the Center of Curvature on a Concave Mirror

"When the rays diverge form a point at a distance from the mirror less than that of the principal focus,…

"The focus of each point chose may be determined by tracing two rays from the point, and locating their real or apparent intersection after reflection by the mirror. The two rays most convenient for this purpose are teh oen that lies along the axis fo the point, and the one that lies parallel to the principal axis of the mirror." -Avery 1895

Concave Mirror with Image and Focus

"The focus of each point chose may be determined by tracing two rays from the point, and locating their…

"When a charge is moved from any point to another point in the same equipotential surface, no work is done upon it. When a charge is moved from one such surface to another, the work done is independent of the path of transfer. If such a surface was to be rendered impenetrable, a particle could lie upon it without tendancy to move along it in any direction. If any two points in such a surface were to be joined by a conductor, no flow of electrification would take place. The closed lines are equipotential lines drawn, upon equipotential surfaces, about two similartly electrified spheres, the quantity of electrifaction at A being twice that at B." -Avery 1895

Equipotential Lines

"When a charge is moved from any point to another point in the same equipotential surface, no work is…

"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…

"Illustration showing the detail of a carbon arc lamp; S, solenoid; c, clutch; w, clutch-washer; T, electromagnet; m, short circuit point; R, resistance properly adjusted." -Avery 1895

Detailed Arc Lamp

"Illustration showing the detail of a carbon arc lamp; S, solenoid; c, clutch; w, clutch-washer; T,…

"A pyramid is a solid whose base is a polygon, and whose sides are triangles uniting at a common point, called the vertex." —Hallock 1905

Pryamid

"A pyramid is a solid whose base is a polygon, and whose sides are triangles uniting at a common point,…

"A cone is a solid whose base is a circle and whose convex surface tapers uniformly to a point." —Hallock 1905

Cone

"A cone is a solid whose base is a circle and whose convex surface tapers uniformly to a point." —Hallock…

"A sphere is a solid bounded by a uniformly curved surface, every point of which is equally distant from a point within, called the center." —Hallock 1905

Sphere

"A sphere is a solid bounded by a uniformly curved surface, every point of which is equally distant…

"In a body free to move, the center of gravity will lie in a vertical plumb-line drawn through the point of support. Therefore, to find the position of the center of gravity of an irregular solid, as the crank, Fig 8, suspended it at some point, as B, so that it will move freely. Drop a plumb line from the point of suspension and mark its direction. Suspend the body at another point, as A, and repeat the process. The intersection C of the two lines will be directly over the center of gravity." —Hallock 1905

Center of Gravity of a Solid

"In a body free to move, the center of gravity will lie in a vertical plumb-line drawn through the point…

"The object W to be lifted is called the weight; the force is represented by P; the point, or pivot, F is called the fulcrum." —Hallock 1905

Lever

"The object W to be lifted is called the weight; the force is represented by P; the point, or pivot,…

"The object W to be lifted is called the weight; the force is represented by P; the point, or pivot, F is called the fulcrum." —Hallock 1905

Lever

"The object W to be lifted is called the weight; the force is represented by P; the point, or pivot,…

"The object W to be lifted is called the weight; the force is represented by P; the point, or pivot, F is called the fulcrum." —Hallock 1905

Lever

"The object W to be lifted is called the weight; the force is represented by P; the point, or pivot,…

"A screw is a cylinder with a helical proection winding around its circumference. This helix is called the thread of the screw. The distance that a point of the helix is drawn back or advanced in the direction of the length of the screw during one turn is called the pitch of the screw." —Hallock 1905

Using a Screw to Raise Weight

"A screw is a cylinder with a helical proection winding around its circumference. This helix is called…

"In some cases it is desired to raise water higher than it can be forced by the pressure of the atmosphere into the chamber of a simple suction pump. To accomplish this the pump chamber with its bucket and valves are set at a distance above the supply not exceeding that to which the air will successfully force the water. A closed pipe, P', called the delivery, or discharge, pipe, is then led from the upper part of the chamber to the point where it is desired to deliver the water." —Hallock 1905

Lifting Pump

"In some cases it is desired to raise water higher than it can be forced by the pressure of the atmosphere…

"At the freezing point [phosphorus] hardens, becomes brittle, and shows, on being broken, evidences of crystalline structure, the crystals being dodecahedral." —Hallock 1905

Phosphorus

"At the freezing point [phosphorus] hardens, becomes brittle, and shows, on being broken, evidences…

"Attach a ball, for instance, to a cord; and , fastening the end of the cord at a point, O, give a quick impulse to the ball. It will be found to move in a circle, ABCD, because the cord keeps it within a certain distance of the centre (sic). Were it not for this, it would move in a straight line." —Quackenbos 1859

Centrifugal Force

"Attach a ball, for instance, to a cord; and , fastening the end of the cord at a point, O, give a quick…

"We have an example of resultant motion in a boat which a person attempts to row north across a river, while the tide carries it to the east. Each force produces the same effect as if acted alone; and the boatman, when he has crossed the river, will find himself neither due north nor due east of the point from which he started, but northeast of it." —Quackenbos 1859

Resultant Motion with Boat

"We have an example of resultant motion in a boat which a person attempts to row north across a river,…

"The part of the body in which the centre of gravity is situated, may be found, in some cases, by balancing it on a point. Thus the centre of gravity of the poker represented [here] lies directly over the point on which it is balanced." —Quackenbos 1859

Center of Gravity

"The part of the body in which the centre of gravity is situated, may be found, in some cases, by balancing…

"When such a surface is irregular in shape, suspend it at any point, so that it may move freely, and when it has come to rest, drop a plumb line from the point of suspension and mark its direction on the surface. Do the same at any other point, and the centre of gravity will lie where the two line intersect." —Quackenbos 1859

Center of Gravity

"When such a surface is irregular in shape, suspend it at any point, so that it may move freely, and…

"As the liquid flows out of each orifice, each stream follows a parabolic path based upon pressure of the liquid inside the container. Orifices A and C are equidistant, thus reach the same point." —Quackenbos 1859

Course of Streams

"As the liquid flows out of each orifice, each stream follows a parabolic path based upon pressure of…

"A card placed at point A receives normal light. At point B the card receives four times as much light, but only at 1/4 intensity. At point C nine times the area covered, but only 1/9 the intensity." —Quackenbos 1859

Light Intensity at Different Distances

"A card placed at point A receives normal light. At point B the card receives four times as much light,…

"Since A is producing light and larger than object B, the shadow of B continuously shrinks to a single point at C." —Quackenbos 1859

Diminish Shadow

"Since A is producing light and larger than object B, the shadow of B continuously shrinks to a single…

Illustration of point of tangency (line and circle).

Point of Tangency

Illustration of point of tangency (line and circle).

Illustration of radius drawn to point of contact of a tangent.

Point of Tangency

Illustration of radius drawn to point of contact of a tangent.