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प्रश्न
Compare resistance and reactance.
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उत्तर
- Resistance:
- Resistance is opposition to the flow of charges (current) and appears in a DC circuit as well as in an AC circuit.
- In a purely resistive circuit, current and voltage are always in phase.
- Resistance does not depend on the frequency of AC.
- Resistance gives rise to the production of Joule heat in a component.
- Reactance:
- The term reactance appears only in an AC circuit. It occurs when an inductor and/or a capacitor are used.
- When reactance is not zero, there is nonzero phase difference between current and voltage.
- Reactance depends on the frequency of AC. In the case of an inductor, reactance increases linearly with frequency. In the case of a capacitor, reactance decreases as the frequency of AC increases; it is inversely proportional to frequency.
- In a circuit with pure reactance, there is no production of heat.
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संबंधित प्रश्न
A 2 µF capacitor, 100 Ω resistor and 8 H inductor are connected in series with an AC source.
(i) What should be the frequency of the source such that current drawn in the circuit is maximum? What is this frequency called?
(ii) If the peak value of e.m.f. of the source is 200 V, find the maximum current.
(iii) Draw a graph showing variation of amplitude of circuit current with changing frequency of applied voltage in a series LRC circuit for two different values of resistance R1 and R2 (R1 > R2).
(iv) Define the term 'Sharpness of Resonance'. Under what condition, does a circuit become more selective?
Is energy produced when a transformer steps up the voltage?
A transformer is designed to convert an AC voltage of 220 V to an AC voltage of 12 V. If the input terminals are connected to a DC voltage of 220 V, the transformer usually burns. Explain.
A capacitor acts as an infinite resistance for ______.
A bulb rated 60 W at 220 V is connected across a household supply of alternating voltage of 220 V. Calculate the maximum instantaneous current through the filament.
A device Y is connected across an AC source of emf e = e0 sin ωt. The current through Y is given as i = i0 sin (ωt + π/2).
- Identify the device Y and write the expression for its reactance.
- Draw graphs showing a variation of emf and current with time over one cycle of AC for Y.
- How does the reactance of the device Y vary with the frequency of the AC? Show graphically.
- Draw the phasor diagram for device Y.
Average power supplied to a capacitor over one complete cycle is ______.
If circuit containing capacitance only, the current ______.
A.C. power is transmitted from a power house at a high voltage as ______.
When an ac voltage of 220 V is applied to the capacitor C, then ______.
An alternating current of 1.5 mA and angular frequency 300 rad/sec flows through a 10 k Ω resistor and a 0.50 µF capacitor in series. Find the rms voltage across the capacitor and impedance of the circuit.
When an AC voltage of 220 V is applied to the capacitor C ______.
- the maximum voltage between plates is 220 V.
- the current is in phase with the applied voltage.
- the charge on the plates is in phase with the applied voltage.
- power delivered to the capacitor is zero.
A resistor of 50 Ω, a capacitor of `(25/pi)` µF and an inductor of `(4/pi)` H are connected in series across an ac source whose voltage (in volts) is given by V = 70 sin (100 πt). Calculate:
- the net reactance of the circuit
- the impedance of the circuit
- the effective value of current in the circuit.
An AC source is connected to a capacitor C. Due to decrease in its operating frequency ______.
A 40 µF capacitor is connected to a 200 V. 50 Hz ac supply. The rms value of the current on the circuit is, nearly ______.
In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?
When an AC voltage of 220 V is applied to the capacitor C ______.
A 10 µF capacitor is connected to a 210 V, 50 Hz source as shown in figure. The peak current in the circuit is nearly ______.
(π = 3.14)
