Question

What do we mean by saying

"Frequency of AC current is 50hz for Indian houhold"?

Answer 1

Frequency is defied as number of cycles per second.
And in case of some of the countries like India; in one second sinusoidal voltage/current completes 50 cycles.
(cycle is repetition of similar par of the waveform, one cycle involves equal positive & negative parts)
.
Hence as supply completes 50 cycles in one second, frequency is said to be 50Hz.
.
Frequency = cycles/sec Hertz