III. Scan the text to match the clauses together to make sentences.

A

1 The line voltage found in a three-phase,WYE-connected system is

2 Because a 120-degree phase difference exists between thevoltages,

3 They add vectorially and

4 In the four-wire, grounded-neutral, WYE-connectedsystem,

5 The three-phase wires run to buses,

6 A bus is a primarypower distribution point that is

7 The connections for loads requiring 120volts are

8 The load connections requiring 208 volts are

B

a between two of the buses (phases).

b between one of the buses and the aircraft frame.

c connected to the mainpower source.

d which supply power to various loads.

e the neutral wire attaches to the frame of theaircraft (ground).

f not directly.

g they reach their peak amplitudes at differenttimes.

h the vector sum of the voltagesgenerated by two separate phase windings.

IV Grammar:Preposition.

Preposition is a part of speech which has no independent lexical meaning of its own. It indicates a relationship between two notional words. If the preposition modifiers a noun, it follows that noun and becomes a part of a noun phrase, when the preposition modifiers a verb, it post modifies that verb.

There are four classifications of prepositions:

Simple prepositions are small single words that occur frequently: at, in, for,

with, by, from, of, to, on.

Derivative – they are formed from other words: across, below, regarding,

considering, depending, behind, along etc.

Compound: inside, without, outside.

Complex prepositions consist of a maximum of four words that occur frequently:

in accordance with, up to, in comparison with, in front of, for the sake of,

on behalf of, except for etc.

Usually prepositions stand between two words to express the relation between them. Sometimes one of the two words takes the initial position or is not used at all. In these cases the preposition is attached to the remaining word.

It occurs in:

· exclamatory sentences. What a beautiful place to live in!

· passive constructions. The doctor is sent for.

· some syntactical patterns with the infinitive or gerund. She is difficult to deal with. It is not worth worrying about.

· some clauses beginning with conjunctive and relative pronouns and in

subordinate contact clauses. What we are thinking of is how she wrote a

test. The man we told you about is our relative.The boy she is in love with studies at our University. It is her talents she relies on.

· special questions, both direct and indirect. They asked me who the looks were for. What bus they go by?

· In some cases the preposition may precede the interrogative or relative words. To whom shall we give this certificate? By what bus will they go?

In abbreviated sentences and clauses consisting only of a preposition and an interrogative word the preposition normally precedes it. – But to whom?

All the prepositions can be divided into the following groups:

Prepositions of time: on, around, about, from, by, for, since, until, at, in, after, before, during, through, till, throughout, within.

Prepositions of movement: into, out of, to, from (point), toward, away from, by (go by, stop by), up, around, across, through, along, in.

Prepositions of position: at, in, between, among, above, over, below, under, beneath, before, behind, on, in, off, on.

Prepositions of place: at, in, on.

Prepositions of manner, agent, instrument and purpose: by, with, in, for.