27的立方根是a,16的算术平方根是b,则ba=______.
∵27的立方根是a,
∴a=3,
∵16的算术平方根是b,
∴b=4,
∴ba=43=64.
故答案为:64.
在如图所示的电路中,电源电压为3V保持不变,定值电阻R的阻值为5Ω,滑动变阻器标有“20Ω 2A”字样,当滑片有A端滑动到B端的过程中( )
A.定值电阻R两端的电压不断变小
B.定值电阻R的功率不断变小
C.滑动变阻器两端的电压不断变小
D.滑动变阻器的功率先变大后变小
To succeed in a scientific experiment _____ .
A.carefulness is need
B.carefulness is one needs
C.one needs to be careful
D.one need being careful