题干

小灯泡 L 的额定电压为 3V,它的 I-U 图像如图甲所示.把小灯泡接入如图乙所示的电路中,先将滑动变阻器的滑片 P 移至 B 端,闭合开关 S,电压表示数为 1.5V;再将滑片 P 向左 移动直到电压表示数为 3V.已知电源电压恒定,滑动变阻器的铭牌标有“10Ω 2A”.下列说法中错误的是(   )

A:电源电压为4.5V

B:电路中消耗的最大功率为 1.35W

C:小灯泡的额定功率为 1.5W

D:小灯泡正常发光时,滑动变阻器消耗的电功率为 0.75W

上一题 下一题 0.0难度 选择题 更新时间:2019-12-13 08:39:43

答案(点此获取答案解析)

B

同类题2

阅读短文,然后根据其内容选择正确答案。

Dear mum and dad,

    I'm writing this letter to you from the center of Australia. At themoment we're staying near Uluru—that's the aboriginal(土著) name for Ayers Rock. On the first day, we took a balloon tour over the rock, and I was surprised at how big it was: 3.6 kilometers long and 384 meters high. The colors of the rock are fantastic, and at different times of the day, they change from purple to red. The Aborigines are the first people of Australia, and the ancient aboriginal stories describe the spirits that created the world. Uluru is a center of Aboriginal culture.

    The Australians have many British relatives. That's why they're like us in many ways. Their family life is similar to ours, and they enjoy the same food and hobbies. The food and drink that most Australians like are grapes, lamb, ham and especially wine that they make in the south of the country. They love all sports, but football is the most popular. Most Australians live near the coast, so they also love going to the beach, swimming and surfing.

Although it's December, it's summer over here. The sunshine is very bright, and near the coast the countryside is very green. There are lots of sheep in the fields and on the hills, but the outback(澳洲内陆) is more like a desert, full of rocks and sand.

    The next day after we arrived at Uluru, we went on a camel(骆驼) ride. The camel that I rode had a bad temper. When I sat on its back, it became very angry and refused me. So everyone else thought it was very funny that my camel kept lying down…

    Finally, later this evening, we're taking the plane back to Sydney and coming home, it's been a fantastic trip!

Tony