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How does the sign of the phase angle phi...

How does the sign of the phase angle `phi`, by which the supply voltage leads the current in an LCR series circuit, change as the supply frequency is gradually increased from very low to very high values.

Text Solution

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The phase angle `phi` by which voltage leads the current in L-C-R series circuit is given by,
`tan phi=(X_L-X_C)/R=(2pivL-1/(2pivC))/R`
`therefore` for `v lt v_r "tan" phi lt 0` and where v=frequency
for `v gt v_r tan phi gt 0 v_r`= resonant frequency
for `v=v_r tan phi=0`
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