磁场具有能量,磁场中单位体积所具有的能量叫做能量密度,其值为
,式中B是磁感强度,μ是磁导率,在空气中μ为一已知常数.为了近似测得条形磁铁磁极端面附近的磁感强度B,一学生用一根端面面积为A的条形磁铁吸住一相同面积的铁片P,再用力将铁片与磁铁拉开一段微小距离△l,并测出拉力F,如图所示.因为F所作的功等于间隙中磁场的能量,所以由此可得磁感强度B与F、A之间的关系为B=______.B2 2μ
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APP具体操作流程为:
刮片细胞学检查时,常用的固定液是()
A.甲醛
B.丙酮
C.乙醇
D.冰醋酸
E.甲醇
根据句子意思,用括号中所给单词的适当形式填空,并将答案填写在标号为 51~56的相应位置上。
小题1:Now more and more (college) students can make money to support their daily life.
小题2:Although he was just 7, he achieved his goal of being a weekly winner (success) in CCTV Avenue of Stars.
小题3:The little boy’s parents promise to take him to the USA on his (nine) birthday.
小题4:All the Chinese look forward to (make) the Chinese Dream come true.
小题5:What a (please) trip to Hongkong he had last summer!
小题6:Thanks for ( invite) me to see such a wonderful movie.
坚持四项基本原则,是我们事业健康发展的根本前提和保证。 ( )
简述霍布斯主权学说的特点。
一般吊装式集装箱船在满载时的GM时的适度值约在范围()内。
A、0.3∽1.0m
B、0.5∽1.2m
C、0.8∽1.2m
D、1.2∽1.6m