The picture above shows an LRCcircuit driven by a sinusoidal voltage source with

Question

The picture above shows an LRCcircuit driven by a sinusoidal voltage source with frequency f. Thevoltage is E, the current is I, and the resonant frequency isfR.

TrueFalse For any f, Irms = Erms/Z.
TrueFalse If f < fR then E lags behind I.
TrueFalse For fixed E, Irms is largest when f =fR.
TrueFalse If f = fR, then E leads I by exactly 90degrees.
TrueFalse If f = fR, then E lags I by exactly 90degrees.
TrueFalse If f > fR, then Xc >Xl. The picture above shows an LRCcircuit driven by a sinusoidal voltage source with frequency f. Thevoltage is E, the current is I, and the resonant frequency isfR.

Explanation / Answer

   a.   TRUE    b.   TRUE             phase angle     =   tan-1{(XL   -   XC)/ R}    since at lower (f < fR),XC is greater than XL making -ve, whichmeans E lags behind I.    c.   TRUE    Irms   =   E/{R2   +   (XL   -   XC)2}    at   f   =   fr,      XL   =   XC    since denominator is minimum atf   =   fr,   Irmsis maximum.    since denominator is minimum atf   =   fr,   Irmsis maximum.    d.   FALSE             =   00    e.   FALSE                =   00    f.   FALSE    as   f   >   fr    XL   >   XC    XL   >   XC

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