【单选题】ZHDY6-2*如图所示,两根导线沿半径方向引向铁环上的A,B两点,并在很远处与电源相连。已知圆环的粗细均匀,电流I,圆环半径R,θ=60°。则环中心O的磁感应强度为()
【单选题】What does IA stand for?
【判断题】Cargo insurance is one of the most important parts in international trade. Insurance policy is an evidence of government policy referring to insurance market.( )
【简答题】There are four persons to be qualified to sign insurance document namely (1) ______ (2) his agent, (3) ______ (4) his agent.
【判断题】重力场中,微粒数量随高度的关系是海拔越高,数量越少。