Advertisements
Advertisements
Question
The reactance of a circuit is zero. It is possible that the circuit contains
(a) an inductor and a capacitor
(b) an inductor but no capacitor
(c) a capacitor but no inductor
(d) neither an inductor nor a capacitor
Solution
(a) an inductor and a capacitor
(d) neither an inductor nor a capacitor
(a) The reactance of a circuit containing a capacitor and an inductor is given by,
`X = X_L - X_C = omegaL - 1/(omegaC)`
if `omegaL = 1/(omegaC) X = 0`. so , the circuit contains an inductor and a capacitor.
(b) For a circuit without a capacitor, reactance is given by,
`X' = X_L = omegaL` which cannot be zero for an AC source.
(c) Similarly, for a circuit without an inductor, reactance is given by,
X" = `Xc = 1/(omega C)`
(d) For a circuit without any capacitor and inductor, reactance, X' = 0 ( L = C = 0)
APPEARS IN
RELATED QUESTIONS
Reactance of a coil is 157 Ω. On connecting the coil across a source of frequency 100 Hz, the current lags behind e.m.f. by 45°. The inductance of the coil is ...........
(a) 0·25 H
(b) 0·5 H
(c) 4 H
(d) 314H
Draw a graph to show variation of capacitive-reactance with frequency in an a.c. circuit.
An inductor L of inductance XL is connected in series with a bulb B and an ac source. How would brightness of the bulb change when (i) number of turn in the inductor is reduced, (ii) an iron rod is inserted in the inductor and (iii) a capacitor of reactance XC = XL is inserted in series in the circuit? Justify your answer in each case.
A capacitor of capacitance 0.5 μF is connected to a source of alternating e.m.f. of frequency 100 Hz. What is the capacitive reactance? (Π = 3.142)
A light bulb and a solenoid are connected in series across an ac source of voltage. Explain, how the glow of the light bulb will be affected when an iron rod is inserted in the solenoid.
A light bulb is rated at 100 W for a 220 V a.c. supply. Calculate the resistance of the bulb.
A light bulb is rated at 120 W for a 220 V a.c. supply. Calculate the resistance of the bulb.
A light bulb is rated at 125 W for a 250 V a.c. supply. Calculate the resistance of the bulb.
A light bulb is rated 100 W for 220 V ac supply of 50 Hz. Calculate
(i) The resistance of the bulb;
(ii) The rms current through the bulb.
When the frequency of the AC source in an LCR circuit equals the resonant frequency, the reactance of the circuit is zero. Does it mean that there is no current through the inductor or the capacitor?
Which of the following plots may represent the reactance of a series LC combination?
(i) An alternating emf of 200 V, 50 Hz is applied to an L-R ciruit, having a resistance R of 10 Ω and an inductance L of 0.05H connected in series. Calculate :
(1) Impedance
(2) Current flowing in the circuit
(ii) Draw a labelled graph showing the variation of inductive reactance (`X_L`) verses frequency (`f`) .
A coil having self-inductance of 0.7 H and resistance of 165 Ω is connected to an a.c. source of
275V,50Hz. If π = `22/7`
Calculate:
(i) Reactance of the coil
(ii) Impedance of the coil ‘
(iii) Current flowing through the coil
The potential difference across the resistor is 160 V and that across the inductor is 120 V. Find the effective value of the applied voltage. If the effective current in the circuit is 1⋅0 A, calculate the total impedance of the circuit.
A series combination of an inductor (L), capacitor (C) and a resistor (R) is connected across an ac source of emf of peak value E0, and angular frequency (ω). Plot a graph to show variation of impedance of the circuit with angular frequency (ω).
Which of the following graphs represents the correct variation of capacitive reactance Xc with frequency v u?
