10. Correct the sentences if it is necessary.
1. Each electric particle projects into space a field of electric force, and as the particles move along a wire, the lines of force move with them.
2. A variable electric field is never accompanied by a magnetic field; and conversely, a variable magnetic field is always accompanied by an electric field.
3. The joint interplay of electric and magnetic forces is what is called an electromagnetic field: it is not distributed continuously in space; in a vacuum it propagates at the speed of light (300 km/sec); it interacts with charges and currents to convert itself into other forms of energy (chemical, mechanical, etc.).
4. The theory of the electromagnetic field was stated by the Scotch physicist James Clerk Maxwell in his "Electricity and Magnetism" published in 1873.
5. In the case of a stationary charged body the magnetic fields, built up by the elementary charges constantly moving inside it cancel each other, and there is magnetic field.
6. A measure of the strength of an electric field is given by the mechanical force per unit charge experienced by a very small body placed in this field and is denoted by the letter F.
7. If the strength of an electric field is the same both in magnitude and direction at any point in space, the field is called nonuniform.
8. It is relevant to note that quantities which have both magnitude and direction are called scalars, as distinct from quantities which have only magnitude and are called vectors.
9. The total number of lines of electric force through a surface placed in an electric field is called the surface charge density and is denoted by the letter N.
10. Placing a negative charge at definite point in the field set up by a positively charged spherical body, it is possible to obtain a set of such paths, or lines of electric force.
11. Like charges are known to attract one another.
12. The surface charge density depends on the quantity of electric charge on a given body and on the shape of the letter.
11. Use the text to answer the following questions:
What is an electromagnetic field?
What properties has the electromagnetic field?
What condition enables us to investigate electric and magnetic fields separately?
What quantities are called vectors (scalars)?
What is an electric flux?
In what way can we determine the electric flux of a uniform field?
What is the strength of an electric field?
What is the surface charge density?
On what does the surface charge density depend?
How is the strength of a magnetic field measured?
12. Put the jumbled sentences in the logical order to sum up the contents of the text.
1. Modern physics defines the electromagnetic field as a distinct form of matter possessing definite properties.
2. The theory of the electromagnetic field was stated by the Scotch physicist James Clerk Maxwell in 1873.
3. If the strength of an electric field is the same both in magnitude and direction at any point in space, the field is called uniform.
4. An inertialess charge placed in an electric field would follow a path called a line of force.
5. It is the motion of these lines of electric force that sets up a magnetic field transverse to them.
6. Typical vectors are force, velocity, acceleration, while typical scalars are temperature, quantity of matter, energy, power.
7. The density of lines of force will give a graphic idea of the field strength.
8. The particles move along a wire, the lines of force move with them.
9. In the case of a stationary charged body the magnetic fields, built up by the elementary charges constantly moving inside it cancel each other, and there is practically no magnetic field.
10 The joint interplay of electric and magnetic forces is what is called an electromagnetic field and is considered to have its own objective existence apart from any electric charges or magnets with which it may be associated.
11. The joint interplay of electric and magnetic forces is what is called an electromagnetic field: it is distributed continuously in space; in a vacuum it propagates at the speed of light (300,000 km/sec); it interacts with charges and currents to convert itself into other forms of energy (chemical, mechanical, etc.).
12. Quantities which have both magnitude and direction are called vectors, as distinct from quantities which have only magnitude and are called scalars.
13. The quantity of electricity per unit area is called the surface charge density.
14. Each electric particle projects into space a field of electric force.
15. A measure of the strength of an electric field is given by the mechanical force per unit charge experienced by a very small body placed in this field and is denoted by the letter E.
16. For a nonuniform field the flux is determined in a different way.
17. The total number of lines of electric force through a surface placed in an electric field is called the electric flux and is denoted by the letter N.
18. It depends on the quantity of electric charge on a given body and on the shape of the latter.