【单选题】已知在 CaF 2 ( K sp = 5.3 × 10 - 9 ) 与 CaSO 4 ( K sp = 9.1 × 10 - 6 ) 混合物的饱和溶液中, c (F - ) = 1.8 × 10 - 3 mol × L - 1 则 CaSO 4 的溶解度为 mol × L - 1 。
【单选题】已知CaF 2 的K sp = 5.3×10 -9 ,在氟离子浓度为3.0 的溶液中Ca 2+ 可能的最高浓度为( )
【判断题】电网中任一瞬间的短路全电流i k 为其周期分量i p 与非周期分量i np 之和。
【单选题】Which of the following is the way that a computer does its processing?
A.
Recognition and computation separately.
B.
Recognition and computation at the same time.
C.
Computation followed by checking.
D.
Recognition, reasoning and then computation.
【判断题】电网中任一瞬间的短路全电流为其周期分量与非周期分量之和。
【单选题】Which of he following is the way that a computer does its processing?
A.
Recognition and computation separately.
B.
Recognition and computation simultaneously.
C.
Computation followed by checking.
D.
Recognition, reasoning and then computation.
【多选题】符合( )条件之一时,数台交流电动机可共用一套短路保护电器。
A.
总计算电流不超过20A,且允许无选择地切断时
B.
根据工艺要求,必须同时起停的一组电动机,不同时切断将危及人身设备安全时
C.
短路保护兼作接地故障保护时,应在每个不接地的相线上装设
D.
当只在两相上装设时,在有直接电气联系的同一网络中,保护器件应装设在相同的两相上
【单选题】Which of the following is the way that a computer does its processing?
A.
Recognition and computation separately.
B.
Recognition and computation simultaneously.
C.
Computation followed by checking.
D.
Recognition, reasoning and then computation.