在爆炸危险范围内，防爆电器设备的金属外壳不应接地。
参考答案：错
如图所示，平行金属导轨与水平面成θ角，导轨与固定电阻R1和R2相连，匀强磁场垂直穿过导轨平面．有一导体棒ab，质量为m，导体棒的电阻与固定电阻R1和R2的阻值均相等，与导轨之间的动摩擦因数为μ，导体棒ab沿导轨向上滑动，当上滑的速度为v时，受到安培力的大小为F．此时（ ）
A．电阻R1消耗的热功率为Fv/3
B．电阻R2消耗的热功率为Fv/6
C．整个装置因摩擦而消耗的热功率为μmgvsinθ
D．整个装置消耗的机械功率为（F+μmgcosθ）v
Which of the following statements describing options is false()
A. A put option gives its holder the right to sell an asset for a specified price on or before the option’s expiration date.
B. A call option will be exercised only if the market value of the underlying asset is more than the exercise price.
C. A put option’s profit increases when the value of the underlying asset increases.
