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【单选题】
用细导线均匀密绕成长为 l 、半径为 a ( l >> a ) 、总匝数为 N 的螺线管, 为真空 .若线圈中载有稳恒电流 I ,则任意一点的A.
磁感强度大小为 B = m 0 NI
B.
磁感强度大小为 B = NI / l
C.
磁场强度大小为 B = m 0 NI / l
D.
磁场强度大小为 B = NI
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举一反三
【单选题】Perseverance is a kind of quality and that is _______ it takes to do anything well.
A.
what
B.
that
C.
which
D.
why
【简答题】自然界的水有三种形态,水蒸气属于 态的水;露、雾属于 态的水;霜、雪、冰属于 态的水。
【简答题】perseverance
【单选题】Nothing lay ahead of us but exertion, struggle, and perseverance. ( Para.16 )
A.
What we are confronted with is no exertion, struggle or perseverance.
B.
The kind of life that was waiting for us at school would be full of exertion, struggle and perseverance.
C.
We would have nothing, no exertion, no struggle or no perseverance.
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