题目

电热的公式?单位?焦耳定律:数学表达式为:Q=____________,电流通过导体做功,若电能全部转化为内能则:Q=W=________=________=________。串联电路中I一定,R越大单位时间内产生的热量越_____。并联电路中,U一定,R越小,I越大(I是平方倍增大)单位时间内产生的热量越______。 答案:【答案】  Q=I2Rt  Pt  UIt  U2t/R  多  多【解析】焦耳定律的表达式:Q=I2Rt;当电能全部转化为内能时,电热等于电功,此时有:Q=W= Pt =UIt=t;在串联电路中,电流处处相等,根据公式Q=I2Rt可知,电阻越大,在相同的时间内产生的热量就越多;并联电路中,各支路两端相等,在相同的时间内根据公式Q=tBody and Food Your body, which has close relations with the food you eat, is the most important thing you own, so it needs proper treatment and proper nourishment (营养).The old saying “An apple a day keeps the doctor away”is not as silly as some people think. The body needs fruit and vegetables because they contain vitamin C. Many people take extra vitamins in pill form, believing that these will make them healthy. But a good diet is made up of nourishing food and this gives all the vitamins you need. The body doesn’t need or use extra vitamins, so why waste money on them? In the modern western world, many people are too busy to bother about eating properly. They throw anything into their stomachs, eating hurriedly and carelessly. The list of illnesses caused or made worse by bad eating habits is frightening, 56. “Your body has close relations with the food you eat.” It really means that ______. A. all kinds of food you eat can be made into your body B. your body is made up of the food you eat C. what you eat has great effect on your health D. the more you eat, the fitter you will feel 57. The old saying referred to in the, passage tells us that ______. A. eating apples regularly does lots of good to our health B. the apple is the best among all kinds of fruits C. apples can take the place of doctors D. an apple is a sure cure for illness 58. In the second paragraph, the writer tries to let us know ______. A. our bodies need food or we can’t live B. often eating apples is a good habit C. taking extra vitamin pills is completely useless D. a good diet is of great importance for our health 59. In the modern western countries ______. A. people don‘t want to pay more attention to their eating B. lots of people’s illnesses are caused or made worse by bad eating habits C. people throw everything into their stomachs without chewing D. people are only too busy to cook meals for themselves 60. From the passage we can draw a conclusion that if we want to keep healthy,we should ______. A. only eat an apple a day B. eat properly C. take as many vitamin pills as possible D. throw something into our stomachs slowly and carefully
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