题干

在如图所示的电路中,电源电压为9V且保持不变,电流表的规格为“0~3A”,电压表的规格为“0~15V”,灯泡上标有“6V 6W”字样,灯泡中的电流随电压变化的关系如图所示.试求:

(1)灯泡正常发光时的电阻.
(2)当电流表示数为0.4A时,电压表的示数.
(3)灯泡正常发光时滑动变阻器消耗的电功率.

上一题 下一题 0.0难度 选择题 更新时间:2018-04-12 09:05:42

答案(点此获取答案解析)

解:根据灯泡的铭牌可以知道,灯的额定电压为6V,额定功率为6W,由功率的计算公式可以变形为P=UI=
U
2
R
,灯正常发光时的电阻为<

同类题3

阅读理解

    Lying alongside mountains of smelly garbage under the South American sun, Cateura is a long way from the conservatories of Prague or Vienna. Yet the township, which grew out of Paraguay's largest dump(垃圾场), is gaining a reputation as a hothouse for musical talent and for its youth orchestra(管弦乐队) that plays instruments made from garbage. "The world sends us garbage. We send back music," says Favio Chavez, leader of the "Recycled Orchestra," during a recent visit by the group to Los Angeles. Orchestra members, poor children from Cateura, play violins fashioned from oven trays and guitars made from dessert dishes. The orchestra provides the youngsters an outlet and an escape, a chance to go beyond the mess of their slum(贫民窟) through the music of Mozart, and even Sinatra. "In the beginning, it was difficult to play," says the l0-year-old violinist Celeste Fleitas." But Favio helped me learn over time. From Favio, I have learned to be more responsible and value the things I have."

    The destination for more than 1,500 tons of waste each day, the community has no safe drinking water and little access to electricity or sanitation(卫生设施). Illiteracy is severe, and the children of the township often fall into drugs, violence and crimes.

    Favio Chavez, a musical talent, came to Cateura as an environmental technician in 2006 and started a youth music school. He knew shop-bought instruments were beyond the means of villagers whose sheds are worth less than a violin, so he approached a carpenter to make some out of waste from the dump.

    The orchestra caught the eye of Paraguayan filmmaker Alejandra Amarilla. She uploaded a short piece of the orchestra to YouTube in 2012, hoping to secure crowdfunding for what would become Landfill Harmonic, a documentary released across the United States this month and promoting the youngsters on a tour of the world's music halls later on.

同类题4

根据短文内容, 从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    Everyone, from homeless people to billionaires, is likely to be influenced by stress; there's simply no way to avoid it ____ Here are five powerful tips for ways to kill stress in almost any situation.

Eat Healthier

    Though a lot of stress is psychological, there are also plenty of physical factors that lead to this natural human response to noticed danger, In order to relieve stress, make sure you're treating your body right. A big part of this is eating healthier ____ Anyway, adopting an alkaline(碱性的)diet instead of an acidic (酸性的)one is recommended.

Wake Up Earlier

    ____ However, waking up 15 or 20 minutes earlier each morning may have more benefits than sleeping in. By giving yourself some extra time, you won't feel quite rushed in the morning, which leads to better preparation and more confidence.

____

    Since you are never going to remove 100 percent of the stress in your life, one of the best things you can do is let it be one of your motivations. This is what stress is designed to do, after all. The psychological and physical reactions brought on by stress are supposed to heighten our senses and empower us to fight off a threat.

Watch a Funny Video

    Here is a simple and practical tip: watch a funny video on You Tube, Research shows that seeing something amusing activates the part of the brain that produces calm physiological(生理的)responses. This can lead to less anxiety and more happiness.

Take Walk Outside

    Whenever possible, make sure you take your walk outdoors ____ It can improve energy levels and memory by as much as 20 percent.

A.A number of studies are two important keys to good health.

B.Diet and relaxation are two important keys to good health.

C.There are no magic”anti-stress”foods.

D.However, there are ways to reduce the amount of stress you suffer from.

E.Keep Positive Relationships

F.Let Stress Motivate You

G.It is certainly true that the more sleep you get, the less stressed you'll be.