In one A.C. generator, brushes connected with slip rings become positive and negative alternatively at the regular interval of 10 ms. Then angular frequency of this A.C. voltage would be ……….

Options

A. 50
B. 100
C. `50pi`
D. `100pi`

Answer

D

Explanation

A.C. voltage can be represented graphically as follow :

We can see that polarity of A.C. voltage changes at every half cycle i.e. at the end of every `T/2` time interval, which is given 10 ms in the statement. Hence,
`T/2`=10 ms
`therefore` T=20 ms = `20xx10^(-3)` s
`therefore (2pi)/omega=20xx10^(-3) (because omega=(2pi)/T)`
`therefore omega=(2pi)/(20xx10^(-3))`
`therefore omega=100pi "rad"/s`