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From General to Specific Worksheet Task 2 Rearrange the following paragraphs so that resultant text follows a general –specific pattern. Faraday and Electro-Magnetism (i) He was familiar with the phenomenon of electric induction. When an electrified body, say a piece of amber, is brought near to an unelectrified body, the forces from the former body separate out the two kinds of electricity in the latter, the further parts becoming charged with electricity of the same sign as that on the amber, and the nearer parts with electricity of the opposite sign; this is why rubbed amber attracts light pieces of paper, or the needle of an electroscope. Faraday knew, too, that a magnet which is brought near to an unmagnetised piece of iron induces magnetism in the latter, so that it and the magnet attract one another; this is why a magnet picks up iron filings. (ii) Faraday, pondering on these facts, wondered whether a current flowing in a circuit might not in the same induce another current in a near-by circuit. He tried, without success, to induce a current in a circuit by means of a magnet or a current in another circuit. In 1831, he wound 203 feet of copper wire round a large block of wood, interspersing another 203 feet of similar wire as a spiral between its turns, and preventing electrical leakage between the two wires by binding both with twine. This gave him two circuits in the closest proximity, with facilities for making a current in one and for observing a current in the other. If the flow of a current in the first circuit induced a current in the second, then the galvanometer1 included in the latter ought to show a deflection. At first, none could be observed but Faraday noticed later a slight instantaneous movement of the galvanometer in the second circuit, just at the moment of starting the current in the first circuit. A similar movement occurred in the reverse direction at the moment when the current was stopped. (iii) In this way the mechanical work of moving a magnet could be made to produce an electrical current. A way had been found to convert mechanical energy into the energy of an electric current. On a larger scale the magnet might be moved by a cola-burning engine, thus transforming the heat energy of coal into the energy of an electric current. The science of electrical engineering had been born. 1 Galvanometer: instrument consisting of a coil of wire surrounding a smalll magnet and pointer. When an electric current passes through the coil it produces a magnetic field at its centre and deflects the magnet. (iv) For out of this fundamental experiment of Faraday has grown the whole vast technology of the mechanical production of electric power, and of the structure and operation of dynamos. The converse procedure of transforming the energy of an electric current into mechanical energy lies at the basis of electric motors and of all forms of electric transport – trains, trams, lifts and so on. (v) Michael Faraday (1791 – 1867) was born in London, the son of a blacksmith and began life as an errand boy for a book-binder. While he was thus employed, a customer gave him tickets for some scientific lectures which Sir Humphry Davy was giving at the Royal Institution. Here he attracted the interest of Sir Humphry, and finally was appointed his lecture assistant. (vi)The secret was now out. No current was induced in the second circuit by a steady current in the first, but one was induced by changes in this current. Once this had been established, it was only a step to see whether the current in the first circuit could be replaced by a magnet, and Faraday soon found that the motion of a magnet in the proximity of a circuit induced a current in the latter. Adapted from The Growth of Physical Science. In English Studies Series 4 (1969). Oxford: O.U.P Answers: (v) (i) (ii) (vi) (iii) (iv)