How to use Magnets in a sentence
He invented magnets that could withstand the effects of percussion and ordinary temperature variations.
It consists of a disk of aluminium, the axis of which is geared to a counting mechanism and which runs between the poles of permanent magnets that create eddy currents in it and therefore exert a retarding force.
The axis of the magnet is horizontal and at the same level as the mirror magnet, while when the central division of the scale B appears to coincide with the vertical cross-wire of the telescope the axes of the two magnets are at right angles.
According to this theory the molecules of any magnetizable substance are little permanent magnets the axes of which are, under ordinary conditions, disposed in all possible directions indifferently.
The magnets hitherto considered have been assumed to have each two poles, the one north and the other south.Advertisement
A magnet may be regarded as consisting of an infinite number of elementary magnets, each having a pair of poles and a definite magnetic moment.
If two magnets having moments M, M' are arranged at right angles to each other upon a horizontal support which is free to rotate, their resultant R will set itself in the magnetic meridian.
At shorter distances the magnetism induced in the weaker magnet will be stronger than its permanent magnetism, and there will be attraction; two magnets with their like poles in actual contact will always cling together unless the like poles are of exactly equal strength.
The effect of the field upon the speed of the revolving electrons, and therefore upon the moments of the equivalent magnets, is necessarily a very small one.
Since the poles of different magnets differ in strength, it is important to agree upon a definite unit or standard of reference in terms of which the strength of a pole may be numerically specified.Advertisement
One of the fragments may again be broken, and again two bipolar magnets will be produced; and the operation may be repeated, at least in imagination, till we arrive at molecular magnitudes and can go no farther.
The distribution of magnetism and the position of the poles in magnets of other shapes, such as cylindrical or rectangular bars, cannot be specified by any general statement, though approximate determinations may be obtained experimentally in individual cases.'
A very pure form of iron, which from the method of its manufacture is called " steel," is now extensively used for the construction of dynamo magnets; this metal sometimes contains not more than 0.3% of foreign substances, including carbon, and is magnetically superior to the best commercial wrought iron.
Ordinarily a substance composed of asymmetrical molecules is paramagnetic, but if the elementary magnets are so conditioned by their strength and concentration that mutual action between them is possible, then the substance is ferromagnetic. In all cases however it is the diamagnetic condition that is initially set up - even iron is diamagnetic - though the diamagnetism may be completely masked by the superposed paramagnetic or ferromagnetic condition.
The term " electricity " is applied to denote the physical agency which exhibits itself by effects of attraction and repulsion when particular substances are rubbed or heated, also in certain chemical and physiological actions and in connexion with moving magnets and metallic circuits.Advertisement
Ampere had already previously shown that a spiral conductor or solenoid when traversed by an electric current possesses magnetic polarity, and that two such solenoids act upon one another when traversed by electric currents as if they were magnets.
Electric magnets of great power were soon constructed in this manner by Sturgeon, Joule, Henry, Faraday and Brewster.
All the space round magnets, currents and electric charges was therefore to Faraday the seat of corresponding lines of magnetic or electric force.
Holmes had made a magneto machine with multiple permanent magnets which was installed in 1862 in Dungeness lighthouse.
This work, which embodied the results of many years' research, was distinguished by its strict adherence to the scientific method of investigation by experiment, and by the originality of its matter, containing, as it does, an account of the author's experiments on magnets and magnetical bodies and on electrical attractions, and also his great conception that the earth is nothing but a large magnet, and that it is this which explains, not only the direction of the magnetic needle north and south, but also the variation and dipping or inclination of the needle.Advertisement
The boots were working like sticky glue or magnets.
The needle (in the modern pattern) is of soft iron, and is kept magnetized in ductively by the action of two permanent steel magnets.
Steel is much more retentive of magnetism than any ordinary iron, and some form of steel is now always used for making artificial magnets.
The process of magnetization consists in turning round the molecules by the application of magnetic force, so that their north poles may all point more or less approximately in the direction of the force; thus the body as a whole becomes a magnet which is merely the resultant of an immense number of molecular magnets.
A well-known example of hysteresis is presented by the case of permanent magnets.Advertisement
A metal which has great retentiveness may at the same time have small coercive force, and it is the latter quality which is of chief importance in permanent magnets.
The distinguishing feature of the first is the steepness of its outlines; this indicates that the induction increases rapidly in relation to the magnetic force, and hence the metal is well suited for the construction of dynamo magnets.
Eschenhagen 2 first designed a set of magnetographs in which this idea of small moment of inertia was carried to its useful limit, the magnets only weighing 1 .
In the Eschenhagen pattern instrument, in which a single quartz fibre is used for the suspension, two magnets are placed in the vicinity of the suspended magnet and are so arranged that their field partly neutralizes the earth's field; thus the torsion required to hold the magnet with its axis perpendicular to the earth's field is reduced, and the arrangement permits of the sensitiveness being altered by changing the position of the deflecting magnets.
In the Eschenhagen form of vertical force balance two deflecting magnets are used to partly neutralize the vertical component, so that the centre of gravity is almost exactly over the support.
Wilde introduced the use of electromagnets for the field magnets.
In 1750 he published at Cambridge a work of some eighty pages entitled A Treatise of Artificial Magnets, in which is shown an easy and expeditious method of making them superior to the best natural ones.
Henry's "quantity" magnets acquired considerable celebrity at the time, from their unprecedented attractive power - one (August 1830) lifting 750 lb, another (March 1831) 2300, and a third (1834) 3500.
In 1835 he combined the short circuit of his monster magnet (of 1834) with the small "intensity" magnet of an experimental telegraph wire, thereby establishing the fact that very powerful mechanical effects could be produced at a great distance by the agency of a very feeble magnet used as a circuit maker and breaker, or as a "trigger" - the precursor of later forms of relay and receiving magnets.
At the age of nineteen, he was articled for five years as clerk to the master of a school in Spital Square, London, with whom at the end of that time he entered into partnership. In 1750 he read a paper before the Royal Society on a method of making artificial magnets, which procured him election as a fellow of the society and the award of the Copley medal.
The magnets are either sintered or directionally cast, and then annealed in a magnetic field.
Ball and socket armatures have metal feet, which can be used on thin set floors with magnets underneath.
Perhaps it's down to the magnets used blah blah blah.
First, it is essential to use the strongest magnets available, preferably neodymium iron boron.
Powerful magnets aimed at the motor cortex have been shown to induce muscles to twitch.
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However, traditional magnets made of iron were too heavy, so this led to the development of extremely high-powered magnets that were lightweight.
To further boost the strength of my magnets I started to wear magnetic insoles.
The repulsive force between like poles of magnets can be used for magnetic levitation which engineers are trying to exploit in modern train systems.
Both bending magnets in the cell cannot be used due to space restrictions on the experimental floor.
The rotor, incorporating permanent magnets, runs in a bore with a gap of just 1mm.
Coral reefs are irresistible magnets to many varieties of fish and support a huge amount of marine life.
Another thing, forget about ceramic magnets on your speakers, to be Fifties you'll need the good ole blue cobalt stuff.
However, due to their high cost they did not gain widespread use and the rare-earth magnets superseded them.
The powerful curved ceramic ferrite magnets contained in Aquamag produce a super field of high magnetic flux.
No threads No wires No magnets use the matchboxes provided or two of your own.
The magnets in the pillow stimulate the brain to produce more melatonin.
We only use the highest grade neodymium healing magnets, which keep their magnetism for ten years.
All the many variants of the basic concept include permanent magnets, spring and coils.
This means the use of small permanent magnets rather than super-conducting types as found in hospital MRI units.
In a double-blind, placebo controlled study, patients were treated with magnets applied to the skin.
Thin polythene sheeting samples may be attached to it securely by means of small magnets.
Simply attach its obscenely powerful magnets to any surface you see fit and marvel at some truly superhuman leverage... .
It was also found that comparatively small magnets were sufficient, and that there was no particular virtue in the closed circuit and electromagnet, but that a small permanent magnet having one pole in contact with FIG.
Hence, when the undulating telephonic currents were made to pass through the apparatus, the constant variation of the friction of the spring caused the deflexions of the diaphragm to vary in unison with the variation of the electric The extreme smallness of the magnets which might be successfully employed was first demonstrated by Professor Peirce of Brown University, Providence, R.I.
Steel magnets of great strength and of any convenient form may be prepared either in this manner or by treatment with an electromagnet; hence the natural magnet, or lodestone as it is commonly called, is no longer of any interest except as a scientific curiosity.
Useful instructions have been furnished by Carl Barus (Terrestrial Magnetism, 1897, 2, II) for the preparation of magnets calculated to withstand the effects of time, percussion and ordinary temperature variations.
Fleming, Magnets and Electric Currents (London, 1898); C. Maurain, Le magnetisme du fer (Paris, 1899; a lucid summary of the principal facts and laws, with special regard to their practical application); Rapports presentes au Congrks international de physique, vol.
In those meters which are compounded - that is, have a shunt coil wound on the field magnets to compensate for the friction of the train - it is important to notice whether the meter will operate or continue operating when there is no current in the series coil, since a meter which "runs on the shunt" runs up a debt against the consumer for which it gives no corresponding advantage.
According to both, induction, instead of inferring from A, B, C magnets the conclusion " Therefore all magnets attract iron," infers from the hypothesis, " Let every magnet attract iron," to A, B, C magnets, whose given attraction verifies the hypothesis.
Secretary cover futon house light of defense previously ordered not as refrigerators magnets.
To distinguish the different types of metal and shiny plastics using magnets and a scrunch test.
The naval officers were drawn to her like magnets, and by the end of the evening she had seamen all over her.
Simply attach its obscenely powerful magnets to any surface you see fit and marvel at some truly superhuman leverage....
Instead, the HTS crystals (made from yttrium barium copper oxide) react individually when they approach the rotor 's permanent magnets.
At got baby!, you'll find mommy and daddy t-shirts, baby onesies, fun baby bibs, special gifts, cards, stickers, magnets and more.
Intimate wear, cards, coffee mugs, clocks, keepsake boxes, stickers, magnets, caps and more are also sold.
Since 2005 there have been 86 injuries and 1 child related death due to magnets.
Babies should never, ever have toys that contain magnets.
Magnets can become loose, dislodge, and become stuck in your baby's throat.
If your baby manages to swallow two or more magnets, they can become attracted to each other through body parts, such as the intestines, causing major injuries that are very hard to diagnose.
If you have older kids with magnetic toys, special care should be taken to keep magnets well out of your infant's reach.
Your premium will skyrocket if you're driving a luxury automobile, because luxury automobiles are theft magnets.
They can attach with magnets, flip-up from the frame or secure with small hooks.
Basically a generator consists of a set of magnets and a conductor like a coiled wire.
The rotor spins the shaft which in turn spins the magnets and voltage is generated in the coil of wire.
Some chalkboard paint is also magnetic, so you can use magnets to hang things on your chalkboard.
They are held in place by powerful magnets so no hardware or adhesive is needed.
These large magnets are made to attach right to the front of your unit and depict bright scenes of laundry being dried on a line outdoors, or soap bubble filled wash baskets.
QuickKutz Squeeze The QuickKutz Squeeze is a handheld die cut tool that uses magnets to hold individual dies in place.
The features of the display board include a white fabric covering, six decorative magnets, six clothespins, and a narrow ribbon to hang photos from.
Photo frames, magnets, and mini-photo albums are all good gender neutral choices.
Wedding save the date magnets are a great way to let guests know about your upcoming celebration long before invitations are in the mail.
Years ago, when families tended to live close together and fewer people moved great distances, save the date cards and magnets were less crucial than they are today.
Many couples opt for save the date magnets instead of formal printed cards with their preliminary wedding information.
With sophisticated printing techniques, magnets can be made in an astonishing range of colors, styles, and designs, making them the perfect way to announce a wedding date while still coordinating with the theme and tone of the event.
The magnet's orientation may also be able to change and couples could select either horizontal or vertical magnets.
When ordering magnets, couples need to take great care to review and proofread the initial copy to ensure there are no typographical errors.
Orders will take from one to four weeks to be printed and shipped to the couple, so be sure to order magnets early enough to account for this timing.
Depending on the size, style, and quantity of the order, magnets generally cost as little fifty cents or up to two or three dollars each.
Wedding save the date magnets are a fun, practical, and convenient way to let wedding guests know about an upcoming celebration so they can plan accordingly.
With a tremendous range of styles available, from fun and quirky designs to sleek, sophisticated magnets, there is a save the date magnet perfect for every couple's special day.
Something else to consider are save the date cards or magnets.
If you are in search of a magnetic bed for your pet, one of the main points you'll need to consider is the gauss rating of the bed's magnets.
While the number of magnets is an important point to consider, size and placement are also significant.
Magnets work cooperatively to form a circuit that works throughout the body.
Many manufacturers recommend that magnets are approximately one inch in diameter, placed approximately four inches apart and no more than one inch from the top surface of the pad.
Magna Mat uses strategically positioned b-polar, ceramic button magnets between two layers of foam in its orthopedic, magnetic pet beds.
Magnet Therapy Magnets features a variety of magnetic products for your pet, including beds, collars and magnetic therapy sets.
Since many pet beds can become flea magnets, this feature is popular with many pet owners.
The beveled, single cutaway body, two piece mahogany neck with jumbo frets, Grover Mini-Rotomatic machine heads, and hand wound Alnico V magnets in the dual humbucker pickups all scream quality.
Ben Chimol is also known for using magnets in his clasps.
The wolves' heart and toes contain magnets so the two halves can become one.
With all the recent worries about lead in toys produced in China, as well as dangerous magnets and other potential problems, choosing organic toys gives you some reassurance that the products you pick for your baby are safe.
For example, pictures of flowers make beautiful photo magnets, or you can use pictures of family and friends to teach the craft of scrapbooking.
The magnets are set into the bridge area and they are extremely strong, so the clip remains on during most activities.
These clip ons secure to your frame with magnets.
These don't attach with magnets the way some do.
Magnetic clip-on technology is always improving, offering stronger magnets and better placement.
The salespeople are always glad to demonstrate the magnets' strength.
These magnets are lightweight and hidden, but they're strong.
Some have magnets while other clip on with feet.
Those with magnets are the easiest for a child to use.
Their glasses use bottom mounted magnets to attach the clip-ons.
Displacement of these magnets has been reported to cause bleeding and perforation of the nasal septum, while accidental swallowing of these magnets may require emergency surgery.
If you have a child trying to learn the alphabet, a set of brightly colored alphabet magnets is a must.
Make sure your child is old enough that the magnets will not present a choking hazard.
Most packages suggest that the magnets are appropriate for ages three and up, but check the exact packaging on the magnets you are considering buying to make sure they are age appropriate for your child.
Intimate wear, cards, coffee mugs, clocks, keepsake boxes, stickers, magnets, caps, and more are also sold.
The handle also controls magnets that keep the spring compressed; releasing it when the toast is cooked to the user's preference.
Visit Relay for Life Store for a wide selection of items including heavy duty magnets that are purple and white and have a magnetic memo holder and rubber grip.
Breast Cancer Awareness Shoppe has a multitude of Relay for Life items including t-shirts, caps, magnets and lapel pins.
The Relay for Life Store has a wide selection of Relay items such as purple and white magnets,notebooks, key chains, drink wear, apparel, mini fans, frames, luggage tags, mouse pads, charms and beach balls.
However, this toy features dry-erase sheets, media magnets, 3D models, interactive activities, and over 600 sounds.
Save the date items such as magnets, calendars, or bookmarks with the impending wedding date printed on them.
Check out the Sanrio Smiles for Chibimaru accessories like magnets and key rings.
They are like two magnets that simply can't be pulled apart.
Print your paper doll creations on magnetic sheets and cut with household scissors to create customized refrigerator magnets.
They can draw, write, or stick magnets all over it.
You can also purchase small round magnets for any games that may need markers.
If you don't like the idea of giving your children small round magnets, cut up window clings will work equally as well on a laminated surface.
During the first few weeks, visiting the welcome activities often results in free book covers, pencils, pens, magnets, and even meals.
Some fake piercing jewelry use magnets to keep the pieces in place, while others are designed to stick to your skin via suction (like fake tongue piercings).
A product called "Bodytalk" offers the temporary tattoo version of those poetry fridge magnets.
The symbol may be found on car magnets, t-shirts, pins, blogs and Facebook profiles.
VistaPrint also offers promotional materials including postcards, holiday cards, letterhead, magnets and brochures.
Press-on tattoos for kids, bookmarks, magnets, small toys for both kids and adults... the possibilities are literally endless.
Mini business card magnets make a great giveaway at booths.
They print everything from brochures to postcards, newsletters, cards, invitations, magnets, door hangers, letterheads and other business items - for a fee.
Work with a company to create customized, logo-printed magnets, cups or napkins to leave behind in the offices you do clean in.
Ever wonder what's behind the rage for Big Paw car magnets?
Owner and designer of Big Paw Designs, Carole Perry helps us understand why Big Paw car magnets rescue is so important for every cat and dog.
Carole's copyrighted designs of key chains, pewter and car magnets, along with treat tins and stickers, can be found at many retail outlets or from her online store.
By purchasing Big Paw car magnets, you are helping to rescue pets all over the United States.
A portion of every sale is donated to rescue organizations, and retailers can also jump on board by selling Big Paw car magnets to help keep dogs and cats in their communities safe.
Car owners can proudly buy and use key chains, pewter magnets, car magnets, and pet stickers to adorn their vehicles in support of animal rescues.
The Big Paw phenomenon has grown since 2002 with magnets and stickers boasting the words Rescue Mom or Rescue Dad, along with other great phrases.
Placing these magnets and stickers on your car will help support the animals we care for so much.
Along with rescue stickers and magnets, Big Paw Designs also offers charms, collars, leashes and great gift ideas.
Car Magnets - These magnets have various sayings designed to proudly support your pet.
The products and designs of Carole Perry and Big Paw car magnets rescue helps animals everywhere.
At the very least, you can have them design clipart for seat cushions and refrigerator magnets.
You can also make your price list special by having it printed onto magnets or reusable stickers that can be attached to a fridge, file cabinet or bulletin board.
You could use cookie cutters as templates for seasonal coasters, magnets, table decorations and much more.
Create paper doll magnets by printing doll images on magnetic sheets purchased from your nearest office supply store.
On the Internet, there are many free patterns for amigurumi candy corn and for related items, such as pot holders and refrigerator magnets.
Use Easter-theme colors in pastels or soft, earthy tones and choose Easter crafts that have a function to them, such as bookmarks, magnets and decorative flowers, so they may be used year round.
You can display your magnets on bulletin boards and the refrigerator throughout the year as well.
Create homemade magnets with any leftover card stock or construction paper or print out colorful Easter images from the computer.
Purchase sheets of magnets the same size as the sheet of paper you are using, trimming both if needed.
Cut out the pictures and use the magnets for the refrigerator or a magnetic craft board.
Create a set of mini magnets with photos of the graduate.
Print the photos, use a peel and stick magnetic sheet and cut the magnets to size.
It seems that some people attract mosquitoes like magnets, while others can trek through moist and tall grasses unscathed.
In Englishspeaking countries the ore is commonly known as magnetite, and pieces which exhibit attraction as magnets; the cause to which the attractive property is attributed is called magnetism, a name also applied to the important branch of science which has been evolved from the study of phenomena associated with the magnet.
Coulomb, who by using very long and thin magnets, so arranged that the action of their distant poles was negligible, succeeded in establishing the law, which has since been confirmed by more accurate methods, that the force of attraction or repulsion exerted between two magnetic poles varies inversely as the square of the distance between them.
Steel, which is well suited for the construction of permanent magnets, is said to possess great " coercive force."
On the other hand, the form of the third curve, with its large intercepts on the axes of H and B, denotes that the specimen to which it relates possesses both retentiveness and coercive force in a high degree; such a metal would be chosen for making good permanent magnets.
As in Hopkinson's experiments, ring magnets were employed; these were wound with primary and secondary coils of insulated platinum wire, which would bear a much higher temperature than copper without oxidation or fusion.
These high values render hardened tungsten-steel particularly suitable for the manufacture of permanent magnets.
Weber's theory, the molecules of a ferromagnetic metal are small permanent magnets, the axes of which under ordinary conditions are turned indifferently in every direction, so that no magnetic polarity is exhibited by the metal as a whole; a magnetic force acting upon the metal tends to turn the axes of the little magnets in one direction, and thus the entire piece acquires the properties of a magnet.
There were said to be " various kinds of magnets, some of which attract gold, others silver, brass, lead; even some which attract flesh, water, fishes; " and stories were told about " mountains in the north of such great powers of attraction that ships are built with wooden pegs, lest.
It takes the form of a small dynamo having an armature and field magnets without any iron core.
Hence the disk will be accelerated until the driving force is balanced by the retarding force due to the induced currents created in the disk by the permanent magnets.
What is known as the method of sines is used, for since the axes of the two magnets are always at right angles when the mirror magnet is in its zero position, the ratio M/H is proportional to the sine of the angle between the magnetic axis of the mirror magnet and the magnetic - = meridian.
Further, to allow of a correction being applied for the finite length of the magnets the whole series of settings is repeated with the centre of the deflecting magnet at 40 cm.
Omitting correction terms depending on the temperature and on the inductive effect of the earth's magnetism on the moment of the deflecting magnet, if 0 is the angle which the axis of the deflected magnet makes with the meridian when the centre of the deflecting magnet is at a distance r, then zM sin B=I+P+y2 &c., in which P and Q are constants depending on the dimensions and magnetic states of the two magnets.
It is, however, possible by suitably choosing the proportions of the two magnets to cause either P or Q to be very small.
Thus it is usual, if the magnets are of similar shape, to make the deflected magnet 0.467 of the length of the deflecting magnet, in which case Q is negligible, and thus by means of deflexion experiments at two distances the value of P can be obtained.
A carefully made ship's compass is usually employed, though in some cases the compass card, with its attached magnets, is made reversible, so that the inclination to the zero of the card of the magnetic axis of the system of magnets attached to the card can be eliminated by reversal.
The magnetism of these two needles is never reversed, and they are as much as possible protected from shock and from approach to other magnets, so that their magnetic state may remain as constant as possible.
Thus the part of B caused by the permanent magnetism of hard iron must be corrected by permanent magnets horizontally placed in a fore and aft direction; the other part caused by vertical soft iron by means of bars of vertical soft iron, called Flinders bars, before or abaft the compass.
His first notable discovery was the production of the continuous rotation of magnets and of wires conducting the electric current round each other.
For one kind of meat we could substitute another; wool could be replaced by cotton, silk or fur; were our common silicate glass gone, we could probably perfect and cheapen some other of the transparent solids; but even if the earth could be made to yield any substitute for the forty or fifty million tons of iron which we use each year for rails, wire, machinery, and structural purposes of many kinds, we could not replace either the steel of our cutting tools or the iron of our magnets, the basis of all commercial electricity.
Tungsten steel, which usually contains from 5 to Io% of tungsten and from 1 to 2% of carbon, is used for magnets, because of its great retentivit.y.
It is possible that, at some remote day, aluminium, or one of its alloys, may become the great structural material, and iron be used chiefly for those objects for which it is especially fitted, such as magnets, springs and cutting tools.
In passing, it may be noted that the cost of the ore itself forms a relatively small part of the cost even of the cruder forms of steel, hardly a quarter of the cost of such simple products as rails, and an insignificant part of the cost of many most important finished objects, such as magnets, cutting tools, springs and wire, for which iron is almost indispensable.
Attached to the pendulum is a coil of fine wire which moves in the field of a pair of magnets.
A, B, C magnets (S) are all magnets whatever (M).
Whately, on the other hand, proposed an inductive syllogism with the major suppressed, that is, instead of the minor premise above, he supposed a major premise, " Whatever belongs to A, B, C magnets belongs to all."
Hence induction cannot be reduced to Aristotle's inductive syllogism, because experience cannot give the convertible premise, " Every S is M, and every M is S "; that "All A, B, C are magnets " is, but that " All magnets are A, B, C " is not, a fact of experience.
Death-dealers operated off a sense of soul radar that pulled them like magnets to the lives that were on Death's list to be ended.
A noticeable feature in the modern A B C indicator, as well as in all modern forms of telegraph instruments, is the adoption of " induced " magnets in the moving portion of the apparatus.
The magnet between the poles of which the rectangular signal coil moves is built up of a number of thin flat horseshoe-shaped permanent magnets of a special quality of steel, and is provided with adjustable pole pieces.
In what is known as the " hybrid " form of recorder the permanent magnets are provided with windings of insulated copper wire; the object of these windings is to provide a means of " refreshing " the magnets by means of a strong current temporarily sent through the coils when required, as it has been found that, owing to magnetic leakage and other causes, the magnets tend to lose their power, especially in hot climates.
C is compensated by permanent magnets athwartships and horizontal; D by masses of soft iron on both sides of the compass, and generally in the form of cast-iron spheres, with their centres in the same horizontal plane as the needles; E is usually too small to require correction; A is fortunately rarely of any value, as it cannot be corrected.
It follows that between two neighbouring magnets, the poles of which are regarded as centres of force, there must always be four forces in action.