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. Inductor and capacitor
B. Resistor and inductor
C. Resistor and capacitor
D. Resistor , inductor and capacitor

Answer

a,d

Explanation

(a,d) Impedance of an LCR circuit is given by
z = `sqrt(R^(2) xx (X_(L) -X_(C))^(2))`
when R resistance
`X_(L)` = inductive reactance = 2`pi` fL
[ f is frequency, L = inductance ]
` X_(C)` = capacitive reactance = `(1)/(2 pi f C)`
[ c is capacitance ]
`therefore " " Z = sqrt( R^(2) + ( 2 pi fL - (1)/(2 pi f C) )^(2) )`
As frequency f increases, Z decreases and as a result, current increases. At resonant frequency, Beyond `f_(0)`, Z angain increases and as a result, current decreases.
the circuit must consist of L and C or R, L and C combination.
Option (a) and (d) are correct.