15. Put the jumbled sentences in the logical order to sum up the contents of the text.
1. The flow of electrons in a conductor is called an electric current.
2. There are several factors that affect resistance.
3. The resistance of most metals varies directly with temperature.
4. That is, temperature being constant, the resistance will be doubled if the length of the conductor is doubled.
5. If two metal spheres on insulating supports are charged with unlike electricity (say, sphere A positively and sphere B negatively) and connected by a metal conductor, electrons will flow from B, where they are in excess, to A where they are lacking.
6. The unit of electrical resistance is the ohm.
7. The resistance of a conductor increases in direct proportion with its length.
8. As a result, energy is released in the form of heat, and the motion of electrons along the conductor is impeded.
9. The resistance in ohms of a conductor 1 metre long and 1 mm2 in cross-section is called resistivity and is designated by the Greek letter p (rho).
10. Resistance varies with the atomic structure or nature of the conducting material.
11. The change in the resistance of a conductor per ohm of the initial resistance and per degree change of temperature is termed the temperature coefficient of resistance and is designated by the letter a
12. The resistance of metals increases with increasing temperature, while that of liquids and carbon decreases.
13. The resistance of the conductor varies inversely with its cross-section area.
14. This opposition to the motion of electrons along the conductor is known as the electrical resistance of the conductor.
15. While in motion along a conductor, electrons collide with other electrons, atoms or molecules.
Follow-up activities
16. Choose the key sentences from the “Electric field and Electric current”. and write them down. Now work in pairs (or in groups). Ask your groupmate(s) to translate your Russian versions of the key sentences into English.
18. You are a guest speaker at the conference devoted to the problems of “Electric field and Electric current”. You were asked to deliver a report on these problems. You can use the information from the texts to speak on the theme suggested.
19. Watch the films and give short summaries in writing. What new information can you learn from them?
THE INFINITIVE
GRAMMAR EXERCISES
1.Fill in the blank with the infinitive with or without "to".
Yukawa expected these particles … a mass of two or three hundred times that of an electron.
a) to have, b) have
Scientists consider transistors __ radio engineering and electronics.
a) to revolutionize, b) revolutionize
I saw them _ measurements with this most precise instrument several times.
a) to make, b) make
He wanted the article __ immediately.
a) to be typed, b) be typed
I felt the device __.
a) to shake, b) shake
The fixed date made us __ with the experiment.
a) to hurry, b) hurry
We found the velocity of particles __ on the strength of the field.
a) to depend, b) depend
The students watched the laser __ with great interest.
a) to operate, b) operate
We know gravity ___ on every particle of a body.
a) to act, b) act
I heard him ___ on this problem at the conference
a) to speak, b) speak