Question

The frequency of direct current (d.c.) is :

(a) 0 Hz (b) 50 Hz (c) 60 Hz (d) 100 Hz

Answer 1

The term DC is used to refer to power systems that use only one polarity of voltage or current, and to refer to the constant, zero-frequency, or slowly varying local mean value of a voltage or current. For example, the voltage across a DC voltage source is constant as is the current through a DC current source.
option (a)