何為直流電與交流電?

直流電 : Direct Current(DC),which means the voltage will not be changed in CRO,no phase,no curve,no ph,difference,less dangerous,such as Batteries.

交流電 : Alternating Current(AC),yu can found it in home electricity,as 220V 50Hz Sinusoidal Wave with have more dangerous,AC Have stationary location casn not portable.

2010-01-27 23:35:28 補充：
the peak value of 220V,50Hz Sinusoidal Wave : 220V x 1.414 = 311.08V,
the tolerance of 220V is 6% = 206.8V - 233.2V

本人試答, 交流電是正弦波; 即是從視波器見到波形有上半波, 零電位, 及下半波的組成. 無論是上半波對零電位的電壓, 或下半波對零電位的的電壓, 都是交流電.
直流電是上半波對零電位之上; 即是不到零電位, 及直流電是下半波對零電位之下, 都是直流電.