物理竞赛讲义12(国外英文资料).docVIP

物理竞赛讲义12(国外英文资料) electromagnetic induction I. knowledge networks or summaries Two, method integration The comprehensive application of electromagnetic induction law involves not only Faradays law of electromagnetic induction, but also knowledge of mechanics, electrostatic field, circuit, magnetic field and so on. There are two basic types of electromagnetic induction problems: one is the synthesis of electromagnetic induction and circuit and electric field; the other is the combination of electromagnetic induction and magnetic field, the force and motion of the conductor, and the two. There are also two basic types of compound problems in which the electromagnetic phenomena and the force phenomena are interrelated, interact and restrict each other. The basic form is the right diagram. Three, focus and hot spot dialysis (1) understanding and application of Lenzs law When using Lenzs law to solve electromagnetic induction, we should pay attention to the following four points: (1) hinder the change of the original magnetic flux or the change of the original magnetic field, and can be used to analyze the direction of induced current and the trend of expansion or contraction of force and area. (2) obstruction of relative motion. Understood as to refuse to leave, can be used to analyze the force and direction of movement. (3) indicates a change in the magnetic flux of the delay. (4) determine the direction of the coil movement. The coil produces an induced current in the magnetic field and is subjected to the action of the magnetic field, causing the coil to move. The force of the coil is determined by the equivalence (the equivalent of the through coil and the bar magnet) and the obstruction. [example 1] AB, shown in figure, is a closed rectangular wire frame that rotates around an axis O perpendicular to the surface. When the slide P of the sliding rheostat slides from left to right, from the paper out of the paper, the wireframe AB will () A. remain stationary, B. coun