VII. Reading and practice.

Exercise 1. Read the text B in 7 minutes without a dictionary and answer the question “What is discussed in the present text?”

Text B.

Electric circuit

The electric circuit is the subject to be dealt with in the present article. But what does the above term really mean? We know the circuit to be a complete path which carries the current from the source of supply to the load and then carries it again from the load back to the source.

The purpose of the electrical source is to produce the necessary electromotive force required for the flow of current through the circuit.

The path along which the electrons travel must be com­plete otherwise no electric power can be supplied from the source to the load. Thus we close the circuit when we switch on our electric lamp.

If the circuit is broken or, as we generally say "opened" anywhere, the current is known to stop everywhere. Hence, we break the circuit when we switch off our electrical devices. Generally speaking, the current may pass through solid conductors, liquids, gases, vacuum, or any combination of these. It may flow in turn over transmission lines from the power-station through transformers, cables and switches, through lamps, heaters, motors and so on.

There are various kinds of electric circuits such as: open circuits, closed circuits, series circuits, parallel circuits and short circuits.

To understand the difference between the following circuit connections is not difficult at all. When electrical devices are connected so that the current flows from one device to another , they are said to be connected in series. Under such conditions the current flow is the same in all parts of the circuit, as there is only a single path along which it may flow. The electrical bell circuit is considered to be a typical example of a series circuit. The parallel circuit provides two or more paths for the passage of current. The circuit is divided in such a way that part of the current flows through one path, and part through another. The lamps in your room and your house are generally connected in parallel.

Exercise 2. Look through the text once more and ask your friend.

1. If a circuit is a complete path?

2. If there are different kinds of circuits?

3. If the current can pass through liquids?

4. If we open the circuit when we switch on the light?

5. If the lamps in the room are connected in series?

Exercise 3. Speak on the difference between:

1. Closed circuits and open circuits.

2. Series circuits and parallel circuits.

Exercise 4. Read the text C for 3 minutes and point out the main idea of each paragraph.

Text C .