JAMB - Physics (1999 - No. 33)
in a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30V and 40V respectively, what is the voltage across the capacitor?
30V
40V
50V
70V
Explication
At resonance, inductive reactant XL is equal to the capacitive reactance XC
i.e. XL = XC
and XL = VL/IL
and XC = VC/IC
Again since the components are in series, the same current flows in the series arrangment
i.e. IL = IC
at resonance, VL/IL = VC/IC
∴ VL = VC
= 40V
i.e. XL = XC
and XL = VL/IL
and XC = VC/IC
Again since the components are in series, the same current flows in the series arrangment
i.e. IL = IC
at resonance, VL/IL = VC/IC
∴ VL = VC
= 40V