Light in the measurement of the output voltage and the input voltage is the same,needs to be connected to more than 20 w load can measure the output voltage.
Alternating current (ac), the output is also an alternating current,it is not a direct current (dc)
The above, said 4000 W, is the point at which work load energy impedance,
Inductive load is 1/3 impedance load,load impedance refers to light, heat wire, etc,Inductive load is only series motor, etc.