Earth’s Magnetic Fields

The Earth’s Magnetic Field is why free-floating magnetic needles come to rest roughly along the geographical north-south axis. It demonstrates that the earth operates as a massive magnetic dipole, with its magnetic poles located close to its geographical poles.

Because the magnetic needle’s north pole approximates geographic north (NG), the magnetic pole near NG is appropriately referred to as the magnetic south pole of Earth. In addition, the pole near SG is the earth’s magnetic north pole (Nm).

The Earth’s Magnetic Field and Magnetic Elements at any point on the earth can be completely defined in terms of specific quantities called magnetic elements of the earth, namely:

• The magnetic variation, which is also known as declination.
• Dip or inclination δ
• Bh denotes the horizontal component of the earth’s magnetic field.

   

Magnetic Fields – Brief Description 

The earth’s magnetic field is equivalent to that of a bar magnet angled 11 degrees from the earth’s rotation axis. The magnetic field was assumed to be due to iron in the core of Earth. The problem with this depiction is that iron’s Curie temperature is roughly 770 degrees Celsius. The core of the earth is hotter and therefore this reasoning is incorrect. So how did the earth get its magnetic field? The magnitude varies over the earth’s surface from 0.3 to 0.6 Gauss.

The earth’s magnetic field is attributed to a dynamo effect of the circulating electric current but is not directionally constant. Rock samples of different ages in similar locations show different directions of permanent magnetization. The earth’s rotation plays a role in creating the currents believed to be the source of the magnetic field. Mariner 2 found that Venus has no such effect. A magnetic field, although its central iron content, should be similar to that of the earth. The rotation period of Venus of 243 earth days is too slow to produce the dynamo effect.

Magnetic Susceptibility Formula

The ratio of the magnetization M within the material to the applied magnetic field strength H, or m = M/H, is the magnetic susceptibility formula of a material, typically indicated by m. The absolute temperature is inversely related to paramagnetic susceptibility. 

m∝1/T   [For paramagnetic materials]

The magnet is primarily classified into three categories:

• Permanent magnet – A magnet made of a permanently magnetized substance that generates its own continuous magnetic field. Magnetizable materials are known as ferromagnetic materials. Materials like iron, nickel, and cobalt are examples.

   

• Temporary magnet – A magnet that is only magnetized for a limited time is known as a temporary magnet. These magnets are often made up of soft materials with low magnetic characteristics. They become magnetized for a brief time when a strong or permanent magnet attracts them.

   

• Electromagnet – An electromagnet is a magnet that generates a magnetic field due to current passing through it. Wire twisted into a coil is the most common electromagnet; as current travels through the wire, a magnetic field is formed inside the coil. When the current is turned off, it goes away. Electromagnets are commonly found in motors, generators, and hard disc drives.

   

Three elements of the earth’s magnetic field

The size, as well as the direction of the earth’s magnetic field, are determined by three elements of the earth’s magnetic field:

• Magnetic declination
• The magnetic inclination or the angle of dip.
• The horizontal component of the earth’s magnetic field.

   

Magnetic Declination

Magnetic declination is the angle formed between the true north and magnetic north. On the horizontal plane, true north is never in the same place and varies based on the location on the earth’s surface and the passage of time.

Magnetic Inclination

The angle of dip is another name for the magnetic inclination. It is the angle formed by the magnetic field with the  horizontal plane on the earth’s surface. The magnetic equator has a 0° angle of dip, while the magnetic poles have a 90° angle of dip.

Horizontal component of the Earth’s magnetic field

The horizontal component of earth’s magnetic field is the component of magnetic field along the earth’s surface. This along with angle of dip can be used to find out the net magnetic field at that point by using simple trigonometry.

Bar magnet

A natural magnet, iron ore magnetite attracts small bits of iron, cobalt, nickel, and other metals. Natural magnets have an uneven form and are ineffective. When a piece of iron or steel is brushed with a magnet, it obtains magnetic qualities. Artificial magnets are magnets constructed of iron or steel. Artificial magnets can be made to have any shape or strength. A bar magnet is an artificial magnet in the shape of a rectangular or cylindrical bar.

Basic properties of magnets

• The filings stick to the magnet’s ends when submerged in iron filings. At the magnet’s two ends, the attraction is greatest. The magnet’s poles are the opposite ends.
• When a magnet is suspended freely, it always points north-south. North Pole N is the pole that points to the geographic north, and South Pole S is the pole that points to the geographic south.
• The magnetic poles are always found in pairs. The isolated magnetic pole, in other words, does not exist. Because the poles of a magnet are positioned slightly inwards from the magnet’s free ends, its magnetic length is always shorter than its geometric length.
• Poles that are similar repel each other, while dissimilar poles attract each other. (We can detect repulsion when the North Pole of one magnet is brought near the North Pole of another magnet, but attraction when the North Pole of one magnet is drawn close to another magnet’s South Pole.)
• Coulomb’s inverse square law describes the force of attraction or repulsion between two magnetic poles. The symbol for pole strength is m, and the unit is an ampere meter.

Conclusion

We have seen the meaning of Earth’s Magnetic Field and Magnetic Elements and its Magnetic Susceptibility Formula, Causes, Categories, Components, and Basic. The Earth’s Magnetic Field and Magnetic Elements at any point on the earth can be completely defined in terms of specific quantities called magnetic elements of the earth. The earth’s magnetic field is believed to play an important role in making the planet habitable. A magnetic field not only determines the direction of our compass needles but also acts as a kind of shield that deflects the solar wind that could otherwise devour the wind.