Exercise 1. Listen to the text and fill in blanks.
There are several different _________ that can supply the voltage ________ to generate an electric current. The two most common ________ are generators and ________ cells.
Generators use mechanical energy, such as water pouring through a dam or the motion of a turbine driven by ________, to produce electricity. The electric _________ on the walls of homes and other _________, from which electricity to operate lights and _________ is drawn, are connected to giant _________ located in electric power _________. Each outlet contains two _________. The voltage between the terminals drives an electric _________ through the appliance that is _______ into the outlet.
Electrolytic cells use __________ energy to produce electricity. Chemical _________ within an electrolytic cell produce a __________ difference between the cell’s terminals. An electric battery __________ of a cell or group of cells connected together.
There are many sources of electric current other than ________ and electrolytic cells. Fuel cells, for example, ______ electricity through chemical reactions. Unlike electrolytic cells, however, ________ cells do not store chemicals and therefore must be constantly refilled.
Certain sources of electric current operate on the __________ that some metals hold onto their electrons more _________ than other metals do. Platinum, for example, holds its ________ less strongly than aluminium does. If a strip of ___________ and a strip of aluminium are pressed together under the proper conditions, some electrons will flow from the platinum to the aluminium. As the aluminium _______ electrons and becomes negative, the platinum loses electrons and becomes _______.
The strength with which a metal holds its electrons varies with _________. If two strips of different metals are ________ and the joint heated, electrons will pass from one strip to the other. Electricity produced ________ by heating is called thermoelectricity.
Some substances emit electrons when they are _______ by light. Electricity produced in this way is called photoelectricity. When ________ is applied to certain crystals, a potential difference _________ across them. Electricity thus produced is called piezoelectricity. Some microphones work on this __________.
Exercise 2. Answer the following questions.
1) What are the sources of electric power?
2) Which forms of energy can be transformed into electric energy?
3) Which devices of mentioned above are used for creating a direct current and which ones for an alternating current?
4) Could you explain principles of action of a transformer, which change a voltage of the electric current?
5) How is it possible to transform the direct current into the alternating one and vice versa?
6) What do you know about the potential series of metals?
7) What are microphones used for?
Exercise 3. Decide whether the following statements are true or false using information from Exercise 1. If you think the statement is false, change to make it true.
1) Any electrochemical element could be refilled or recharged.
2) Some outlets of the walls contain 3 or even more terminals.
3) Electrolytic cells as well as fuel cells use chemical reactions to produce electric energy.
4) Piezoelectric cells use the energy of falling water to create the alternating current.
5) Generators can not be used for producing a direct electric current.
6) Platinum has negative charge being immersed into solution of electrolyte together with aluminium.
7) Platinum holds some electrons more weakly than aluminium does.