题干

用两只电流表按如图所示实验探究电功率与电流的关系,下列说法正确的是(   )

A:小灯泡电功率的大小是通过灯泡的亮度来判断的,是应用了控制变量法

B:将电灯泡并联是为了控制灯泡两端电流相同

C:选用的两只小灯泡规格必须相同

D:将其中一只电流表移到干路上也可以完成实验

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D

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    You can't always predict a heavy rain or remember your umbrella. But designer Mikhail Belvaev doesn't think that forgetting to check the weather forecast before heading out should result in you getting wet. That's why he created Lampbrella, a lamp post with its own rain sensing umbrella.

    The designer says he came up with the idea after watching people get wet on streets in Russia. “Once, I was driving on a central Saint Petersburg street and saw the street lamps lighting up people trying to hide from the rain. I thought it would be appropriate to have a canopy(伞蓬)built into a street lamp,” he said.

    The Lampbrella is a standard-looking street lamp fitted with an umbrella canopy. It has a built-in electric motor which can open or close the umbrella on demand. Sensors(传感器)then ensure that the umbrella offers pedestrians(行人) shelter whenever it starts raining.

    In addition to the rain sensor, there's also a 360° motion sensor on the fiberglass street lamp which detects whether anyone's using the Lampbrella. After three minutes of not being used, the canopy is closed.

    According to the designer, the Lampbrella would move at a relatively low speed, so as not to cause harm to the pedestrians. Besides, it would be grounded(埋地线) to protect from possible lightning strike. Each Lampbrella would offer enough shelter for several people. Being installed(安装) at 2 meters off the ground, it would only be a danger for the tallest of pedestrians.

    While there are no plans to take the Lampbrella into production, Belyaev says he recently introduced his creation to one Moscow Department, and insists his creation could be installed on any street where a lot of people walk but there are no canopies to provide shelter.