As the frequency of an ac circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the circuit ?

Options

A. incuctor and capacitor
B. Resistor and inductor
C. Resistor and capacitor
D. Resistor, inductor and capacitor

Answer

A, D

Explanation

Reactane of an inductor of inductance L is, `X_(L) = 2pivL`
Where v is frequency of the AC circuit.
`X_(c)`= Reactance of the capacitive circuit
`=1/(2pi//C)`
On increasing frequency v, clearly `X_(L)` increases and `X_(C)` decreases.
For a L-C-R circuit.
Z= impedance of the circuit
`=sqrt(R^(2)+(X_(L)^(2)-X_(C))^(2)`
`=sqrt(R^(2) + (2pivL-1/(2pivC))^(2)`
As frequency (v) increases, Z decreases and at certain value of frequency known as resonant frequency `(v_(0))`, impedance Z is minimum that is `Z_("min")=R` current varies inversely with impedance and at `Z_("min")` current is maximum.