EXERCISE A : Rephrasing Rewrite the following sentences, replacing the words in italics with expressions from the passage which have similar meanings:
1.The flow of the free electrons is an electric curent.
2.Materials in the first group are called conductors. 3.Materials which provide a path for an electric current are conductor. 4.All insulators permit some flow of electrons. 5.Germanium sometimes acts as an insulator and sometimes as a conductor.
EXERCISE B: Contexsual reference
What do the pronouns in italics in these sentence refer to?
1.All materials can be classified into three groups according to how readily they permit
an electric current to flow.(line)
a)three groups
b)all materialsc
c)free electrons
2.Under certain conditions they allow a current to flow easily but under others they
behave as insulator.(line)
c) insulator
3.These are knowns as thermistors.(line)
a)metallic oxides
c)metallic oxides
4.They are therefore used in temperature-sensing devices.(line 20)
c)metallic oxides
EXERCISE C : Checking facts and ideas
Decide if these statements are true or false . Quote from the passage to support your
1. Electrons flow from positive to negative.
2.Copper provides an easy path for an electric current.
3.All metals are good conductors.
4.All good conductors are metals.
5. Air is not a perfect insulator.
6.Rubber readily releases electrons. 7.The resistance of a thermistor is higher at low temperatures than at high temperatures.