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electric current |
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electric current) A simple moving-coil meter. Direct electric current (DC) flowing through the wire coil combined with the presence of a magnetic field causes the coil to rotate; this in turn moves a pointer across a calibrated scale so that the degree of rotation can be related to the magnitude of the current. ) The patterns produced by a direct current and an alternating current on the screen of an oscilloscope. Flow of electrically charged particles through a conducting circuit due to the presence of a potential difference. The current at any point in a circuit is the amount of charge flowing per second; its SI unit is the ampere (coulomb per second). Current carries electrical energy from a power supply, such as an electrical cell (battery), to the components of the circuit, where it is converted into other forms of energy, such as heat, light, or motion. It may be either direct current or alternating current. Heating effectWhen current flows in a component possessing resistance, electrical energy is converted into heat energy. If the resistance of the component is R ohms and the current through it is I amperes, then the heat energy W (in joules) generated in a time t seconds is given by the formula:Magnetic effectA magnetic field is created around all conductors that carry a current. When a current-bearing conductor is made into a coil it forms an electromagnet with a magnetic field that is similar to that of a bar magnet, but which disappears as soon as the current is switched off. The strength of the magnetic field is directly proportional to the current in the conductor - a property that allows a small electromagnet to be used to produce a pattern of magnetism on recording tape that accurately represents the sound or data stored. The direction of the field created around a conducting wire may be predicted by using Maxwell's screw rule.Motor effectA conductor carrying current in a magnetic field experiences a force, and is impelled to move in a direction perpendicular to both the direction of the current and the direction of the magnetic field. The direction of motion may be predicted by Fleming's left-hand rule (see Fleming's rules). The magnitude of the force experienced depends on the length of the conductor and on the strengths of the current and the magnetic field, and is greatest when the conductor is at right angles to the field. A conductor wound into a coil that can rotate between the poles of a magnet forms the basis of an electric motor. |
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| Application of a gentle electrical current to the scalp, which nudges sleepers into a particular phase of sleep, boosts recall the next day for recently learned facts, say neuroscientist Jan Born of the University of Lubeck in Germany and his colleagues. The benefits to automakers are numerous, including reduced packaging size, improved reliability (the average LED has a life of 10,000 hours, compared to 1,000 hrs for an incandescent bulb), fuel economy benefits from lower electrical current usage and weight reductions, along with increased options in lighting design. The Electrodeposition painting process involves vehicle bodies being immersed in a paint tank, with an electrical current passing through the steel parts causing the paint to adhere to the metal surfaces. |
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Electrical current