初三下册物理知识点：电功电功率.doc

初三下册物理知识点：电功电功率 初三下册物理知识点：电功电功率 1电流做功的过程就是电能转化为其它形式能的过程，电流做了多少功，就转变成了多少其它形式的能。 2能量的转化：电灯亮电能转化为热能，再由一部分热能转为光能电动机转：电能转化为机械能。电池充电电能转化化学能光电池工作：光能转化为电能。 3电功：电流所做的功叫电功。计算公式：=电流在某段导体上所做的功，等于这段电路两端的电压、电路中的电流和通电时间的乘积。 功的单位：焦耳度1度=*10焦耳 4电能表的作用：电能表是测量电器在某段时间内所消耗电能的千瓦时数。电能表上”2205”的意义是正常工作电压是220伏，最大工作电流是5安 5电功率：电流在单位时间内所做的功叫做电功率。 计算公式：= 电功率等于电压与电流的乘积. 电功率是用来表示电流做功快慢的物理量。 6额定电压：用电器正常工作时的电压叫额定电压。 额定功率：用电器在额定电压下的功率叫做额定功率。 在低于额定电压下的电压下工作的用电器不能发挥其实际功率。 在高于额定电压的电压下工作的用电器容易被大电流烧毁。 7会画用伏安法测定电灯泡功率的实验图 8”220-25”的意思是：普通照明灯泡，额定电压220伏，额定功率：25瓦”220-100”的灯泡在110伏的电压下工作时，电功率是多少? 91840年英国物理学家焦耳推出了焦耳定律：电流通过导体产生的热量跟电流的平方成正比，跟导体的电阻成正比跟通电时间成正比。 计算公式：= 10电热器的主要部分是发热体，发热体是用电阻率大、熔点高的电阻丝制成 11电热器散热的方法：1加散热窗2加大散热面积3加大空气流通 daily morning exercises or class-break setting-up exercise and discipline inspection and appraisal of public signs;2, daily cleaning and inspection;3, the daily student school appearance, dress, wearing school card check;4, the daily duty guide to the leadership class discipline three rounds.Weekly moral education work:L, the flag raising ceremony and the national flag speech under the flag raising ceremony held on Monday;2, every week a class meeting, the meeting;3, every week two exercises, cleaning and hygiene, behavior norms, attendance situation published cloth appraisal, and the issue of the code of conduct;;4, weekly work week.Monthly moral education work:1, at least once a month, the theme of education activities, to patriotism education, behavior norms of education as the focus, combined with major retreat day.2, the monthly class quantization assessment and class teacher assessment, selection of behavior for the standard model class.Moral education in each term:1, at the end of each semester to form three good student, outstanding student cadres, civilized student.2, at least once a semester, parents will be.,Student etiquette conventionA, the school leavers1, dress neatly to wear school card, step posture correct, full of spirit; cycling of the same students, at the s