A voltage , `E=60 sin(314t)`, is applied across a resistor of `20 Omega`. What will be the reading of `I_(rms)`.
(a) in an ac ammeter?
(b) in an ordinary moving coil ammeter in series with the resistor?

Explanation

Given that `E=60 sin (314 t)`
(a) An ac ammeter will read the rms value
`E_(rms)=(E_0)/(sqrt(2))=(60)/(sqrt(2))=42.2V`
`I_(rms)=(E_(rms))/(R )=(42.4)/(20)=2.12A`
Therefore, ac ammeter will read 2.12A.
(b) An ordinary moving coil ammeter will read the average value of alternating current. since the average value of ac is zero. This meter will give zero reading.