Advertisements
Advertisements
Question
What is the reactance of a capacitor connected to a constant DC source?
Advertisements
Solution
The reactance of a capacitor is given by,
`X_c = 1/{wc}`
For a DC source, ω = 0
⇒ `X_c = 1/(0xxc) = ∞ `
So, for a constant DC source, reactance of a capacitor is infinite.
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
You are given three circuit elements X, Y and Z. When the element X is connected across an a.c. source of a given voltage, the current and the voltage are in the same phase. When the element Y is connected in series with X across the source, voltage is ahead of the current in phase by π/4 . But the current is ahead of the voltage in phase by π/4when Z is connected in series with X across the source. Identify the circuit elements X, Y and Z. When all the three elements are connected in series across the same source, determine the impedance of the circuit.Draw a plot of the current versus the frequency of applied source and mention the significance of this plot.
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.
An AC source is connected to a capacitor. Will the rms current increase, decrease or remain constant if a dielectric slab is inserted into the capacitor?
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?
(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
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?
In a series LCR circuit, VL = 40 V, VC = 10 V, VR = 40 V, and current amplitude is 10\[\sqrt 2\] A. Find the impedance.
In a series RL circuit, VR = 200 V and VL = 150 V. Find the applied voltage.
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?
