有些材料在低温下电阻会消失而成为超导体,当电流通过超导体时,超导体两端的电压为______ ,消耗的功率为_____ ,放出的热量为______ 。
零;零;零
It’s important for us to be healthy.But how can we keep healthy? First,you should eat fruit and vegetables three or four times a week.Then eat sonic tofu every day because it’s good for people,both the young and the old Milk is also necessary(必要的),especially for women.So you should have milk twice a day.It can help you to be strong Next,doing more exercises is better.You can do morning exercises or evening exercises.After supper you should take a walk.
小题1:You should eat ______ three or four times a week.
A.fruit and fish
B.vegetables and mutton
C.tom
D.fruit and vegetables小题2:Tofu is good for______.
A.young people
B.old people
C.young and old people
D.students小题3:Why do the people have milk?
A.It’s delicious.
B.It‘s a drink.
C.It‘s bad for you.
D.It can help you keep strong.小题4:You should have milk _______.
A.Four times a day
B.five times a wee
C.twice a day
D.twice a week小题5:The passage mainly tells us _____.
A.how to keep healthy
B.what health is
C.Why health is important
D.how often you can eat tofu
如图所示abcd为一边长l、具有质量的正方形刚性导线框,位于水平面内,bc边中串接有电阻R,导线的电阻不计。虚线表示一匀强磁场区域的边界,它与线框的ab边平行,磁场区域的宽度为2l,磁感应强度为B,方向竖直向下。线框在一垂直于ab边的水平恒定拉力F作用下沿光滑水平面运动,直至通过磁场区域。已知ab边刚进入磁场时,线框便为匀速运动,此时通过R的电流大小为i0,则从导线框刚进入磁场到完全离开磁场的过程中,流过电阻R的电流i的大小随ab边的位置坐标x变化的图线可能是
A.
B.
C.
D.