Magnetism

The term “magnetism” is derived from “magnesia”, the name of a region in Asia Minor where lodestone, natural magnetic iron ore, was found in ancient times. The Chinese observed the effects of magnetism as early as¹ 2600 BC² when they saw that stones like magnetite, when freely suspended, had a tendency to point a north and south direction.

Magnetism is hard to define – we all know what its effects are: the attraction or repulsion of a material by another material. But why does this happen? And why do we only see it in some materials, notably metals and particularly iron? The physics behind this³ is too complex to go into here⁴, but it is useful to remember that magnetism is a fundamental force (like gravity) and it arises due to the movement of electrical charge. Magnetism is seen whenever⁵ electrically charged particles are in motion.

Materials that are attracted by a magnet, such as iron, steel, nickel and cobalt, have the ability to become magnetized. These are called magnetic materials.

There are two kinds of magnet: the permanent magnet and the electromagnet (temporary magnet). A permanent magnet is a material that, when inserted into a strong magnet field, will not only begin to exhibit a magnetic field of its own, but also continue to exhibit a magnetic field when it is removed from the original field.

Magnetic fields from permanent magnets arise from two atomic sources: the spin and orbital motion of electrons. Therefore, the magnetic characteristics of a material can change when alloyed with other elements. For example, a non-magnetic material such as aluminium can become magnetic in materials such as alnico or manganese-aluminium-carbon.

Did you ever do the famous experiment at school where you took a magnet, placed it on a piece of paper and then sprinkled iron filings over it? If you did, you would see⁶ that it looks a bit like the diagram based on a bar magnet (Figure 7).

Fig. 7. Bar magnet

 

Each one of these lines is called a line of magnetic flux and has the following properties:

· they will never cross, but become distorted,

· they will always try to return to their original shape,

· they will always form a closed loop,

· outside the magnet they run north and south,

· the higher the number of lines of magnetic flux, the stronger the magnet.

The strength of the magnetic field at any point is calculated by counting the number of lines we have at that point and this is then called the flux density measured in webers per square metre. This unit is given the title of a tesla. We define this by saying that: “If one weber of magnetic flux is spread evenly over a cross-sectional area of one square metre, then we have a flux density of one tesla (1T)”. In other words the flux density depends on the amount of magnetic flux lines and the area to which they are applied.

 

Notes

¹ as early as – ще у

² BC – до нашої ери

³ behind this – що стоїть за цим

⁴ to go into here – щоб тут розбиратися з нею

⁵ whenever – кожного разу, коли

⁶ would see – бачили

 

2. Now read the text once again looking up any word you do not understand in a dictionary and answer the following questions.

1. Where is the term magnetism derived from?

2. When did the Chinese observe the effects of magnetism?

3. Why does magnetism happen?

4. What materials are called magnetic?

5. What is a permanent magnet?

6. Under what condition can magnetic characteristics of a material change?

7. How is the flux density calculated?

8. What does the flux density depend on?

 

3. Decide if these statements are true or false. Quote from the text to support your decisions.

1. Lodestone is a natural magnet.

2. It is easy to define magnetism.

3. The scientific concept of magnetism is as important as the concept of gravity.

4. An electromagnet is a type of magnet whose magnetic field is produced by the flow of electric current.

5. Tesla is a unit of a cross-sectional area.

 

Pronounce correctly

 

4. Read the words paying attention to the stress l:

l Ÿ lodestone cobalt alloy carbon paper filing weber tesla

Ÿ l Chinese observe effect suspend assume define remove arise

l Ÿ Ÿ magnetism natural magnetite tendency notably permanent density evenly

Ÿ l Ÿ continue exhibit atomic distorted

 

5. Read the following polysyllable words.

Discovery, phenomenon, especially, majority, ability, diameter, essentially, mechanical, alternative, substantially.

 

Increase your vocabulary

 

6. Find these words and word combinations in the text and try to remember them:

 

assume cross cross-sectional area density exhibit filing flux fundamental happen

lodestone observe ore original permanent spin (spun, spun) spread (spread, spread) suspend term

 

Suffixes say a lot

7. The suffixes – ful (meaning full of) and –less (meaning free from) turn nouns into adjectives.

Example:

use – користь useful –корисний useless - некорисний

Make adjectives from the nouns given below according to the example and translate them.

Power, force, colour, thought, change, pain, grace, success, taste, care, truth, meaning.

8. Which liquid is colourless, odourless and tasteless?

What is useless without electricity?

 

9. What part of the speech are these words? What meaning does the suffix –icshave?Translate the words.

Physics, dynamics, electrostatics, electronics, mathematics, acoustics, kinematics, dynamics, mechanics, cybernetics, thermodynamics, aerodynamics, genetics, politics, economics.

 

10. Choose the word which best completes each sentence.

 

a. Physics b. physical c. physicist

 

1. Wilhelm Eduard Weber is a famous German ____. 2. Isaac Newton’s achievements in mathematics, optics, and ____ laid the foundations for modern science and revolutionized the world.
3. Weight and volume are considered to be the ____ properties of a substance.

 

d. Dense e. densely f. density

 

4. We know flux ____ to be the magnitude of a magnetic, electric, or other flux passing through a unit area. 5. Oxygen is quite a ____ gas. 6. Monaco is the world’s most ____ populated country and second-smallest independent nation.

 

g. Power h. powerful i. powerless

 

7. Computers are now more compact and ____. 8. 30,000 homes were left without ____. 9. Any person who is unable to control or influence events is ____.

 

11. Match the word in A with its definition in B.

 

A	B
1. Physics     2. Electrostatics   3. Mathematics   4. Economics	a. the study of quantity, structure, space, and change   b. the social science that studies the production, distribution and consumption of goods and services   c. the branch of science which studies matter and energy and how they interact with each other   d. the branch of science that deals with the phenomena arising from stationary or slow-moving electric charges.

 

12. Match the words in A with the words which have similar meaning in B.

A. Ancient, to derive from, to continue, to exhibit, to spin, flux, original, loop, title, to calculate.

B. Circle, old, to go on, primary, to rotate, to count, flow, to show, to come from, name.

 

13. Put across or through into the gaps.

1. It is necessary to do the following: to measure the current in the circuit and to measure the voltage ____ the circuit. 2. An ammeter is always placed in series with the resistance or other circuit components ____ which the current is to be measured. 3. A voltmeter is always placed in parallel with the resistance or apparatus ____ which the potential difference has to be measured. 4. In a series connection the charges must go ____ every device, and the energy given to the charges by the power source must be divided between the devices. 5. Ohm’s law states that for a given conductor the current is proportional to the voltage ____ the ends of that conductor. 6. An electromagnet is produced where there is an electric current flowing ____ a conductor, as a magnetic field is produced around the conductor. 7. The resistance of a conductor is the ratio of the potential difference ____ it to the current flowing through it.

 

Word range

14. Which sentence best illustrates the use of the word in italics taken from the text?

1. The term “magnetism” is derived from “magnesia”, the name of a region in Asia Minor…

a. A cross-sectional area is an important term in mechanics.

b. The academic year consists of two terms: autumn term and spring term.

c. His term of office as President is 5 years.

2. Materials that are attracted by a magnet, such as iron, steel, nickel and cobalt, have the ability to become magnetized

a. 98 per cent of the mined iron ore is used to make steel.

b. I need to iron my dress.

c. Steam iron is an electric iron that emits steam from holes in its flat surface.

d. Iron is a strong, hard magnetic silver-grey metal, the chemical element of atomic number 26.

 

Revise your grammar

 

15. Complete the text with the correct form of the verb given in brackets.

Every magnet (1) ____ (have) two poles. This is where most of its magnetic strength (2) ____ (be) the most powerful. These poles (3) ____ (call) north and south. When the north pole of one magnet is placed near the north pole of another magnet, or the south pole (4) ____ (place) near the south pole of the other magnet, the poles (5) ____ (repel). When the north and south poles of two magnets are placed near one another, they (6) ____ (attract) to each other. The attraction or repulsion of two magnets towards one another (7) ____ (depend) on how close they are to each other and how strong the magnetic force is within the magnet. The longer the distance between the magnets is, the less they are attracted to or repelled by one another. When a magnet (8) ____ (break) into little pieces, north and south poles will appear at the broken faces. Each piece (9) ____ (have) its own north and south poles.

 

16. Translate the following sentences paying special attention to the Infinitive and its constructions.

1. All circuits to be worked on must be tested to ensure they are dead. 2. If there appears to be a malfunction during the operation of the meter, the following steps should be performed to isolate the cause of the problem. 3. A conductor for which this relationship is true is said to obey Ohm’s law. 4. Specialists consider an electromagnet to be useful in cases where a magnet must be switched on or off. 5. He seems to know English well.
6. Materials such as rubber are good insulators and are used in appliances and home wires to keep the electricity from creating a short circuit. 7. Large electromagnets are known to be used for sorting metals, picking up old cars and other huge pieces of scrap iron and steel (scrap iron and steel – металобрухт). 8. Here is an example to help you understand what is going on. 9. We know magnetism to be the force where objects are attracted to or repelled by one another. 10. Resistors are said to be in parallel when they are placed side by side and their corresponding ends are joined together.

 

17. Translate the sentences with the gerund.

1. Using this appliance in an environment with a strong radiated radio-frequency electromagnetic field may influence its measuring accuracy. 2. Switch on the multimeter by pressing “Power” switch. 3. It is impossible to solve the problem without understanding the difference between weight and mass. 4. In semiconductors the electrical conductivity can be increased by adding small amounts of some chemical elements. 5. You cannot even think of becoming an electrician unless you have a sound knowledge of the atomic theory of matter.