Question

An alternating current of frequency 60 hz has a

maximum value of 120 amp. Write down the

equation for its instantaneous value. Reckoning

time from the instant the current is zero and

becomes positive. Find:

 the instantaneous value after 1/360 sec.

 the time taken to reach 96 amp for the first

time.

Answer 1

Answer:

Explanation:

Given An alternating current of frequency 60 hz has a  maximum value  of 120 amp. Write down the  equation for its instantaneous value. Reckoning

time from the instant the current is zero and  becomes positive. Find the instantaneous value after 1/360 sec.  time taken to reach 96 amp for the first

time.

We know that v = 120 sin 2πft

                            = 120 sin 2 x π x 60 x t

                            = 120 sin (120 x π x 1/360)

                           = 120 sin (120 x 180 x 1/360)

                    So v = 120 sin 60

                    So v = 103.9 v

Now for second equation we have

96 = 120 x sin 2 x 180 x 60 x t

96 = 120 x sin 360 x 60 t

96/120 = sin 360 x 60 t

360 x 60 t = sin^-1 0.8

                = 53 degree

Now t = θ / 2πf

           = 53 / 360 x 60

           = 0.00245 secs

Answer 2

Answer:

see solutions carefully & using formula