Task 1. Discuss with a partner.
1. Do you agree or disagree with the quotation above?
2. What is electricity? What is magnetism? Is there any connection between them? Are there examples of electricity, magnetism, electromagnetism around us?
Task 2. Scan the text «Magnetism in Nature» and match the information below with the numbers.
| a) Ancient people were familiar with magnetite | |
| b)The North Magnetic Pole doesn’t correspond with the North Pole | 2,000 |
| c)The magnetic poles tend to vary daily | |
| d)The South Magnetic Pole doesn’t correspond with the South Pole | 500,000 |
| e)The magnetic poles sometimes reverse themselves | 1,600 |
Magnetism in Nature
Most modern applications of magnetism use electromagnetism, which is created using electricity. However, there are several natural occurrences of magnetism.
Lodestone, or magnetite, was the first naturally occurring magnetic material to be discovered by man. Over 2,000 years ago, the Greeks, Romans, and Chinese all knew of lodestones and their magnetically attractive properties. Lodestones are composed of iron (chemical symbol Fe) and Oxygen (O) and have the composition Fe3O4. Lodestones are commonly found in nature, and have been found in large quantities in Scandinavia, South Africa, and the United States, as well as other places. Lodestones are among the strongest natural magnets, but they are relatively weak as compared to the synthetic magnets used in everyday life.
The strongest magnet on the Earth is actually the Earth itself! Although scientists are not absolutely certain of what causes the Earth’s magnetic field, they think it is caused by the liquid outer core of the Earth. This is mostly iron, and scientists believe it flows in currents; the motion of the molecules in these currents is theorized to create the Earth’s magnetic field. The Earth’s magnetic poles are not at the same places asthe geographic poles. The North Magnetic Pole is actually in far northern Canada, about 800 miles from the North Pole, and the South Magnetic Pole is off the coast of Antarctica, about 1,600 miles from the geographic South Pole. The magnetic poles tend to wander a bit, sometimes as much as 50 miles in a day. This is due to the interaction of the Earth and the solar wind. In addition to the daily variations, the Earth’s magnetic poles sometimes reverse themselves, with the North Magnetic Pole becomes south and vice versa. When this happens, the Earth’s magnetic field changes direction (and the sale of compasses increases dramatically). This happens about every 500,000 years.
Speaking of compasses, why do compasses point north? The needle of a compass is actually a small permanent magnet. The «north» tip of the compass needle is the north pole of its magnet, and is attracted to the North Magnetic Pole. The north pole of the magnet should not be attracted to the North Magnetic Pole if both are north poles. Similar poles should repel each other, yet the north pole of the compass magnet does indeed point «north». In reality, what we call the North Magnetic Pole is actually the South Pole of the Earth’s magnetic field! Similarly, the so-called South Magnetic Pole is actually the North Pole.
The Earth’s magnetosphere is a region above the Earth’s surface containing charged particles that are affected by the Earth’s magnetic field. It plays an important role in one of nature’s most picturesque magnetic phenomena, the auroras. Sunspots emit a large number of high-energy charged particles, some of which make their way through the Earth’s magnetosphere. These articles create an overload of charged particles in the lower Van Allen belt, which is basically a belt of radiation trapped around the earth. These excess charged particles enter the atmosphere near the Earth’s magnetic poles and collide with gas molecules in the atmosphere. These collisions make the molecules emit energy in the form of visible light. This happens for many molecules; their resulting light display is an aurora. In the northern hemisphere this display is called the Aurora Borealis, or northern lights. The equivalent southern lights are called the Aurora Australis.
Naturally occurring magnets are not used much these days.
(From Electricity and magnetism by John D. Carpinelli)