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UNIT 4Task 1. Study new words and word combinations
TASK 2. Read the text and translate it from English into Russian. An electric circuit or network is a pathway through which the electric current can flow. A simple circuit consists of a power source, two conducting wires, each one attached to a terminal of the source and a device through which electricity can flow. This device is called a load and it's attached to the wires. If all the parts are properly connected, the current flows and the lamp lights up. This kind of circuit is called 'closed'. On the contrary, if the wires are disconnected the circuit is called 'open' or 'broken'. The circuit can be opened and closed by a device called a switch. Loads can turn electrical energy into a more useful form. Some examples are: light bulbs, which change electrical energy into light energy; electric motors, which change electrical energy into mechanical energy; speakers, which change energy into sound. The source provides the electrical energy used by the load. It can be a storage battery or a generator. The switch interrupts the current delivered to the load by the source and allows us to control the flow. When an abnormally high amount of current passes through a network, you get a short circuit. This may occur when there is a drop in the resistance or a broken insulation. In order to prevent short circuits, it is best to use fuses, which melt when too much current flows through them, interrupting in this way the circuit. TASK 3. Match the words with their definitions.
TASK 4. Read the text again and answer the following questions. 1. What does a simple circuit consist of? 2. What happens to the lamp in a closed circuit? 3. Can you name some examples of loads? 4. What is a generator? 5. What is the function of a switch? 6. When does a short circuit occur? 7. What can we use to prevent short circuits? 8. How does a fuse work? TASK 5.Complete the text with the words from the box. Then listen and check.
The 1) … of a circuit can be wired in two different ways: series or parallel. If components are arranged one after another to form a single 2) … between the terminals and the components, the circuit is known as a series circuit. In this type of circuit, the 3) … flows from the negative terminal to the 4) … terminal, passing through all the components of the circuit. This means that the 5) … of energy passing through all the components in the series is the same. The main disadvantage of a series circuit is that when a single component in the path 6) …, the entire circuit stops operating (e.g. Christmas tree lights). A parallel circuit consists of several paths connecting the different components. Each separate path is called a 7) … of the circuit. Current from the source divides and flows through the different branches. Unlike series circuits, if one of the components in the parallel circuit burns out, the other paths 8) … to operate. Parallel circuits are commonly used to connect 9) … at home, so that each socket can function independently. For example, you don't have to 10) … the light in your room for the TV socket to work. TASK 6. Read the text and find synonyms for the following words: excessive, loading up, reacting to high temperatures, adjusted, to melt, clients. A fuse can be added to an electric circuit to protect it from the effects of undue power. This safety device, which is made of a heat-sensitive alloy, is connected in series with the circuit it has to protect. If an excessive amount of current flows through the circuit, the alloy will liquefy and open the circuit. A circuit breaker is fundamental in a house to protect circuits against overloading, overheating and short circuits. The advantage of a circuit breaker is that it can be reset after the overloading by replacing the fuse. A professional electrician should always provide his customers with a map of the electric circuit in the house so that it will be easier to work on it in case of faults. |