Where is a bar magnets pull the strongest

What can you say about the magnetic properties of the refrigerator door near the magnet? Do refrigerator magnets stick to metal or plastic spoons? Do they stick to all types of metal?

You have one magnet with the north and south poles labeled. How can you use this magnet to identify the north and south poles of other magnets? We have thus seen that forces can be applied between magnets and between magnets and ferromagnetic materials without any contact between the objects.

This is reminiscent of electric forces, which also act over distances. Electric forces are described using the concept of the electric field, which is a force field around electric charges that describes the force on any other charge placed in the field. Likewise, a magnet creates a magnetic field around it that describes the force exerted on other magnets placed in the field.

As with electric fields, the pictorial representation of magnetic field lines is very useful for visualizing the strength and direction of the magnetic field. If you place a compass near the north pole of a magnet, the north pole of the compass needle will be repelled and point away from the magnet. Thus, the magnetic field lines point away from the north pole of a magnet and toward its south pole.

Magnetic field lines can be mapped out using a small compass. The compass is moved from point to point around a magnet, and at each point, a short line is drawn in the direction of the needle, as shown in Figure Joining the lines together then reveals the path of the magnetic field line. Another way to visualize magnetic field lines is to sprinkle iron filings around a magnet. The filings will orient themselves along the magnetic field lines, forming a pattern such as that shown on the right in Figure This simulation presents you with a bar magnet and a small compass.

Begin by dragging the compass around the bar magnet to see in which direction the magnetic field points. Note that the strength of the magnetic field is represented by the brightness of the magnetic field icons in the grid pattern around the magnet. Use the magnetic field meter to check the field strength at several points around the bar magnet.

You can also flip the polarity of the magnet, or place Earth on the image to see how the compass orients itself. With the slider at the top right of the simulation window, set the magnetic field strength to percent. Now use the magnetic field meter to answer the following question: Near the magnet, where is the magnetic field strongest and where is it weakest? When two magnets are brought close together, the magnetic field lines are perturbed, just as happens for electric field lines when two electric charges are brought together.

Bringing two north poles together—or two south poles—will cause a repulsion, and the magnetic field lines will bend away from each other. This is shown in Figure When opposite poles of two magnets are brought together, the magnetic field lines join together and become denser between the poles. This situation is shown in Figure Like the electric field, the magnetic field is stronger where the lines are denser.

Thus, between the two north poles in Figure Conversely, the magnetic field lines between the north and south poles in Figure A compass placed here would quickly align with the magnetic field and point toward the south pole on the right.

The density of the magnetic field lines in Figure The density does not indicate the force between the two magnets that create the field. The magnitude of the force between the two magnets is the same in both cases in Figure This can be understood by imagining that you place one of the magnets in the field of the other magnet.

This situation is symmetrical: The magnetic fields look the same—other than direction—for both situations shown in Figure Because the magnets are of equal strength, they perturb the magnetic field of the opposite magnet, which is why the magnetic field must be probed by a small magnetic such as, a compass.

Note that magnets are not the only things that make magnetic fields. Early in the nineteenth century, people discovered that electrical currents cause magnetic effects. The first significant observation was by the Danish scientist Hans Christian Oersted — , who found that a compass needle was deflected by a current-carrying wire. This was the first significant evidence that the movement of electric charges had any connection with magnets.

An electromagnet is a device that uses electric current to make a magnetic field. These temporarily induced magnets are called electromagnets.

Electromagnets are employed for everything from a wrecking yard crane that lifts scrapped cars to controlling the beam of a km-circumference particle accelerator to the magnets in medical-imaging machines see Figure The magnetic field created by an electric current in a long straight wire is shown in Figure The magnetic field lines form concentric circles around the wire. The direction of the magnetic field can be determined using the right-hand rule. This rule shows up in several places in the study of electricity and magnetism.

Applied to a straight current-carrying wire, the right-hand rule says that, with your right thumb pointed in the direction of the current, the magnetic field will be in the direction in which your right fingers curl, as shown in Figure If the wire is very long compared to the distance r from the wire, the strength B of the magnetic field is given by.

The SI unit for magnetic field is the tesla T. This video describes the magnetic field created by a straight current-carrying wire. It goes over the right-hand rule to determine the direction of the magnetic field, and presents and discusses the formula for the strength of the magnetic field due to a straight current-carrying wire.

A long straight wire is placed on a table top and electric current flows through the wire from right to left. If you look at the wire end-on from the left end, does the magnetic field go clockwise or counterclockwise? Now imagine winding a wire around a cylinder with the cylinder then removed.

The result is a wire coil, as shown in Figure This is called a solenoid. To find the direction of the magnetic field produced by a solenoid, apply the right-hand rule to several points on the coil. You should be able to convince yourself that, inside the coil, the magnetic field points from left to right. In fact, another application of the right-hand rule is to curl your right-hand fingers around the coil in the direction in which the current flows. Your right thumb then points in the direction of the magnetic field inside the coil: left to right in this case.

Each loop of wire contributes to the magnetic field inside the solenoid. Because the magnetic field lines must form closed loops, the field lines close the loop outside the solenoid. The magnetic field lines are much denser inside the solenoid than outside the solenoid. The resulting magnetic field looks very much like that of a bar magnet, as shown in Figure The magnetic field strength deep inside a solenoid is.

Use this simulation to visualize the magnetic field made from a solenoid. Be sure to click on the tab that says Electromagnet. You can drive AC or DC current through the solenoid by choosing the appropriate current source.

Use the field meter to measure the strength of the magnetic field and then change the number of loops in the solenoid to see how this affects the magnetic field strength. In other words, a charge moving through the magnetic field produced by another object should experience a force—and this is exactly what we find. As a concrete example, consider Figure The magnitude F of the force experienced by this charge is.

The direction of the force may be found by using another version of the right-hand rule: First, we join the tails of the velocity vector and a magnetic field vector, as shown in step 1 of Figure The direction in which the right thumb points is the direction of the force. For the charge in Figure The only conceivable purpose to build such a submarine was to give the Soviet Union first-strike capability, because this submarine could sneak close to the coast of the United States and fire its ballistic missiles, destroying key military and government installations to prevent an American counterattack.

A magnetohydrodynamic drive is supposed to be silent because it has no moving parts. Instead, it uses the force experienced by charged particles that move in a magnetic field. Facebook Facebook Twitter Twitter. Featured Video. Cite this Article Format. Helmenstine, Anne Marie, Ph. Strongest and Weakest Parts of a Magnet. Understanding the Earth's Two North Poles. What Is Magnetism? Definition, Examples, Facts. The Compass and Other Magnetic Innovations.

Measuring Plate Motion in Plate Tectonics. The Relationship Between Electricity and Magnetism. Dipole Definition in Chemistry and Physics.

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Products What is the strongest type of magnet? What is ferrofluid? How should I dispose of ferrofluid? How strong is flexible magnetic tape and sheet? Can I stick other types of magnets to flexible magnetic sheet or tape? Can I cut your flexible sheet and tape magnets? Can you print on to to your flexible sheet and tape magnets? Can you supply monopole magnets? Applications Which magnets should be used for magnetic therapy?

Which magnets are best for making fridge magnets? Which magnets are best suited for glass wipe boards? Health and safety Which magnets are best suited for children to use? Children should always be supervised when playing with magnets. Neodymium magnets are too strong for children and small neodymium magnets are very dangerous if a child swallows more than one as they can attract in the intestines requiring immediate surgery.

Small alnico magnets are strong enough for children to experience magnetism without a risk of trapping fingers. For example the traditional alnico horseshoe magnet and educational alnico bar magnets are widely used in schools throughout the UK.

These magnets are also available in sets with iron filings to demonstrate the invisible magnetic fields; Horseshoe set - Bar Magnet Set.

Back to top. The way a pacemaker responds to a magnetic field differs between manufacturers and therefore people with pacemakers should not put strong magnets close to their chest. For full health and safety advice, please see our health and safety page. Small and medium sized magnets should not have any detrimental effect on your smartphone or tablet.

It is quite possible that these devices already contain small magnets which enable them to perform certain functions. However, it is always wise to keep large, powerful magnets away from any electronic device as strong magnetic fields could possibly damage mechanical parts. For more information, please read our blog post — will a magnet damage my smartphone? It is possible for the tiny components of mechanical wrist watches to become magnetised when placed in closed proximity to strong magnetic fields if the parts are made from ferrous material.

If the mechanical ferrous parts become magnetised, they can attract to each other, attract to the inside of the casing causing the watch to run fast or slow or cease working altogether. To be on the safe side, you should always keep your mechanical watch away from strong magnetic fields.

If your watch does become magnetised, a watch repair shop should be able to demagnetise it and return it to its correct operation. A permanent magnet is a solid material that produces its own consistent magnetic field because the material is magnetised.

Unlike permanent magnets, the magnetic field exerted by an electromagnet is produced by the flow of electric current. The magnetic field disappears when the current is turned off. Typically, an electromagnet consists of many turns of copper wire which form a solenoid. When an electric current flows around the solenoid coil, a magnetic field is created. If an iron core is inserted into the bore of this solenoid, then magnetism is induced into it and it becomes magnetic, but when the current stops flowing it immediately becomes nonmagnetic.

There are five types of modern permanent magnets , each made from different materials with different characteristics. The strongest magnets, referred to as rare earth magnets , are commonly known as neodymium magnets which are made from an alloy of neodymium, iron and boron NdFeb and samarium cobalt magnets which are made from samarium, cobalt and small amounts of iron, copper and other materials.

Other types of permanent magnets include ferrite magnets, made from a compound of ceramic material and iron oxide SrO. To find out more about each type of permanent magnet, follow the links below:. Samarium cobalt.

Flexible rubber. The pole of a magnet is the area which has the greatest magnetic field strength in a given direction. Each pole is either north facing or south facing. If you break a magnet into two pieces each piece will still have a north pole and a south pole.

No matter how small the piece of magnet is, it will always have a north pole and a south pole. Despite some claims on the internet there is no such thing as a monopole magnet. Both the north pole or south pole of a magnet are equal in holding power and both will stick to magnetic material such as steel or iron. The like poles of two magnets e. We supply self-adhesive and countersunk magnets with either pole on the magnetic face. There are several ways to identify the poles of a magnet, the simplest is to use a compass or an analogue or digital pole identifier.

If you have a smartphone, you can also download our Virtual Pole Tester app , which will identify the polarity of the face of a magnet pointing at your phone. This is why when you hold a compass to a magnet the needle will point to its south pole using the convention that like poles repel and opposite poles attract. Iron powder and filings are perfect for sprinkling onto a sheet of A4 paper to show the magnetic fields lines produced by a magnet.

Simply place the magnet under the paper and watch the filings move around to show the magnetic field lines of any given magnet. Iron powder and filings are our recommended choice of magnet accessories for schools and universities. See our full range in our Science and education magnets section or try our horseshoe set and bar magnet set. Rare earth magnets are made out of the rare earth group of elements in the periodic table and are famous for their strength.

The most common are neodymium-iron-boron NdFeb and samarium cobalt SmCo varieties. What does the "N rating" of a neodymium magnet refer to? There are many different grades of neodymium commercially available ranging from N35 to N55, along with other high-temperature variations. Generally speaking, the higher the grade, the stronger the magnet. Most magnets can be bonded in place with two-part epoxy adhesives. We recommend Araldite Rapid which sets hard in about 5 minutes.

We also recommend Loctite Industrial strength Adhesive which has a similar setting time. Both these have a proven track record of reliably bonding magnets to most surfaces with the exception of certain polythene type plastics.

You should never attempt to cut or drill a magnet as most magnets excluding flexible magnets are very hard and brittle due to the manufacturing process. These magnets cannot be drilled with HSS drills or even carbide drills, they need to be drilled or cut with diamond tooling and plenty of coolant as the dust is flammable.

The grindings are magnetic and within a few seconds of drilling the whole magnet will look like a hedgehog due to the grindings being attracted to the magnet. It is much better to specify a hole which can be manufactured in and magnetised afterwards. Each type of permanent magnet is made in a different way but each will include a process of casting, pressing and sintering, compression bonding, injection molding, extruding, or calendaring processes.

To find out more about how each type of magnet is made, follow the links below:. How are neodymium magnets made? How are samarium cobalt magnets made? How are ferrite magnets made? How are alnico magnets made? How are flexible magnets made? How a permanent magnet works is all to do with its atomic structure.

All ferromagnetic materials produce a naturally occurring, albeit weak, magnetic field created by the electrons that surround the nuclei of their atoms. These groups of atoms can orient themselves in the same direction and each of these groups is known as a single magnetic domain.