题干

一个用半导体材料制成的电阻器D,其电流I随它两端电压U的关系图象如图(a)所示,将它与两个标准电阻R1R2并联后接在电压恒为U的电源两端,三个用电器消耗的电功率均为P,现将它们连接成如图(b)所示的电路,接在该电源的两端,设电阻器D和电阻R1R2消耗的电功率分别是PDP1P2,它们之间的大小关系有(   )

A:P1=4PD

B:P1<4P2

C:PDP2

D:PDP/4

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答案(点此获取答案解析)

B

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Roald Dahl was one of the most successful writers of children's books. He sold millions of books all over the world. Many of his books have been made into films and videos. He is so famous that there is even a Roald Dahl Museum you can visit.

Roald Dahl was born in 1916 in Wales, Britain. His father was rich but he died when Roald was very young. Roald and his mother lived a hard life. He had to leave school and went to Africa where he worked for an oil company.

    In 1939 Roald became a pilot, but he had a bad accident. It made him limp(瘸的) for the rest of his life. After this, Roald went to America where he wrote a story about his experience as a pilot. It was so good that it was put in a magazine.

       Roald married an American film star. They bought a house in England and had five children. From 1960 to 1965,    ▲   : Theo, one of his children, was hit by a taxi and was seriously hurt. Olivia, one of Roald’s daughters, died of a strange illness. Soon after this, his wife also had a serious illness. It took her years to get completely better.

 Gradually Roald became more and more successful. He always did his writing in an old shed(棚) at the back of his house. He always sat in the same old armchair with a wooden board on his lap.

 “One of the nice things about being a writer,” he once said, “is that all you need is what you’ve got in your head and a pencil and a bit of paper.”

       In 1983 Roald wona big prize for his book The BFG. During his life, Roald wrote many famous books, such as Charlie and the Chocolate Factory, Matilda, Fantastic Mr. Fox

       After he died in 1990, Roald left money to help people with serious illnesses and those with problems with reading and writing.