An a.c. voltage is represented by
`E = 220 sqrt2 cos (8 pi) t`.
How many times will the current become zero in 1 sec ?

Answer

8

Explanation

Compare `E = 220 sqrt2 cos (8 pi) t` with the standard form: `E = E_(0) cos omega t`
`omega = 8 pi = (2 pi)/(T) :. T = (2 pi)/(8 pi) = (1)/(4) sec`.
In `(1)/(4) sec`., current becomes zero, twice
`:.` In 1 sec., current will become zero 8 times