题干

关于导体的电阻,下列说法中正确的是()

A:根据公式R= 可知,导体两端的电压、通过导体的电流决定导体电阻的大小

B:当温度一定时,长度不同的两条镍铬合金导线,它们的电阻相等,则长度较长的导线横截面积较大

C:忽略温度的影响,导体电阻的大小由导体的长度和横截面积决定

D:忽略温度的影响,两根长度相同的铝导线,电阻一定相等

上一题 下一题 0.0难度 选择题 更新时间:2019-05-09 02:45:07

答案(点此获取答案解析)

B

同类题2

任务型阅读

    Here's how yo-yo dieting affects your body and your mind

    Yo-yo dieting, also known as weight cycling, occurs when a person experiences periods of weight loss followed by weight gain followed by weight loss and so on and so on. The effects of this weight cycling are significant, even when the weight lost and gained is as little as 10 pounds.____

    It can make you gain weight

    While dieting may help you lose a few pounds at first, it only works temporarily. Your body responds to the lack of calories by turning to lean muscle mass for energy. Once you have returned to your normal eating habits, the weight comes back on –____

    ____

    Yo-yo dieting may increase the risk for heart disease and sudden death in post-menopausal(绝经后期)women. Studies found that when normal-weight women experienced periods of weight cycling, they were 3.5 times more likely to have sudden death than women whose weight remained stable. In the same study, yo-yo dieting increased a woman's risk of death by 66 percent.

It can be damaging to your skin

    Dermatologist (a doctor who studies and treats skin diseases) Robin Evans weighed in on the effect that yo-yo dieting has on the skin. “The up and down weight losses and gains can have harmful effects on the skin especially on the face with stretching and contracting the skin,” said Evans____.

It plays games with your mind

    Yo-yo dieting is hard on the body,____ Repeatedly gaining and losing weight can leave dieters feeling more depressed about their weight and losing self-belief as a result.

    If you're a yo-yo-dieter, talk to your health care provider about lifestyle changes that can help you maintain a stable and healthy weight for years to come.

A. It only works temporarily

B. It can damage your heart

C. but in the form of fat, not muscle

D. but it's even harder on the mind

E. but with a smaller size, you will make yourself less friendly

F. The result ends up more wrinkles and an overall effect of aging the skin

G. We turned to the experts to find out how yo-yo dieting can affect your body and your mind