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# Revision Exercises

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I. Translate from English into Russian the following sentences.

1. When flowing through a conductor the alternating current reverses its direction at regular intervals. The force driving round the armature of the meter is proportional to the product of the strength of two currents, one of which is the current going to the circuit being measured, and the other of which is proportional to the terminal voltage of the circuit being metered. The friction between the wax and the flannel must have rubbed off some electrons of the flannel molecules and left them on the surface on the wax. The nature of the material determines the ease with which electrons are allowed to pass. The voltage may have been too high, the insulation being broken down.

2. Should the temperature of the filament increase, the magnitude of the electron flow will increase. It should be noticed that every atom of matter is charged with minute particles of negative electricity which are called electrons. The grid must be at a higher potential than that of the filament or the electrons would be drawn to it. Such a coil arrangement would tend to make the circuit unstable since there would be possibility of feedback of energy from the plate current to the grid circuit through the tube interelement capacity. Care should be taken that proper values are applied.

3. Providing all the requirements were wet, the efficiency of the apparatus would be increased. Had the conductors been moved up and down so as to cut the line of flux of the magnetic field between the poles the magnets, an e. m. f. would have been generated at the two ends of the conductors. The electric current will flow through s conductor such as copper wire, if the two ends of the wire are maintained at a difference of potential. If a natural magnet were suspended by a string from its centre so that it were free to turn, the magnet would be found to turn until the axis through its poles is lying north and south.

4. Practically all metals are conductors of electricity, the conductivity ranging from silver, which is 1, 06 times as effective as copper, to steel, which has only about 0.1 times that copper. Being allowed to come into contract with the rod, the pith ball is repelled by the rod. When a steel knitting needle is stroken from one end to the other with a piece of lodestone, using for the point of contact one of the points at which the iron filings adhere more freely, the needle acquires the property of attracting iron filings and of setting itself north and south when suspended.

5. Emitting a beta particle does not alter the mass number. Hammering, bending or twisting an iron rod when it is near a magnet increases its magnetization. Many substances after being rubbed behave as amber does. Even the best conductors of electricity offering some resistance to the current flow must be kept in mind while dealing with electrical phenomena. Electromotive force is defined as the work per unit charge done by the battery or generator on the charges in moving them around the circuit.

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