Energy in a current carrying coil is stored in theform of [1988]
In a region of uniform magnetic inductionB = 10^{–2} tesla, a circular coil of radius 30 cm andresistance π^{2} ohm is rotated about an axis whichis perpendicular to the direction of B and whichforms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating currentinduced in the coil is [1988]
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In the circuit of Fig, the bulb will become suddenly bright if [1989]
In which of the following, emission of electronsdoes not take place [1990]
The time constant of C–R circuit is [1992]
In an a.c. circuit, the r.m.s. value of current, i_{rms }is related to the peak current, i_{0} by the relation
An LCR series circuit is connected to a source of alternating current. At resonance, the applied voltage and the current flowing through the circuit will have a phase difference of [1994]
In an experiment, 200 V A.C. is applied at theends of an LCR circuit. The circuit consists ofan inductive reactance (XL ) = 50 Ω, capacitivereactance (XC ) = 50 Ω and ohmic resistance (R)= 10 Ω. The impedance of the circuit is[1996]
In an A.C. circuit with voltage V and current I the power dissipated is [1997]
The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. Theprimary is connected to an A.C. supply of 20 V,50 Hz. The secondary will have an output of [1997]
A stepup transformer operates on a 230 V lineand supplies a load of 2 ampere. The ratio of theprimary and secondary windings is 1 : 25. Thecurrent in the primary is [1998]
An inductance L having a resistance R is connected to an alternating source of angular frequency ω. The quality factor Q of the
inductance is [2000]
A capacitor has capacity C and reactance X. Ifcapacitance and frequency become double, thenreactance will be [2001]
In a series resonant circuit, having L, C and R as its elements, the resonant current is i. The power dissipated in the circuit at resonance is [2002]
A coil of 40 henry inductance is connected inseries with a resistance of 8 ohm and thecombination is joined to the terminals of a 2 voltbattery. The time constant of the circuit is [2004]
In a circuit, L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45°. The value of C is [2005]
A coil of inductive reactance 31 Ω has aresistance of 8 Ω. It is placed in series with acondenser of capacitative reactance 25Ω. Thecombination is connected to an a.c. source of110 volt. The power factor of the circuit is[2006]
The core of a transformer is laminated because [2006]
A transistoroscillator using a resonant circuitwith an inductor L (of negligible resistance) anda capacitor C in series produce oscillations offrequency f. If L is doubled and C is changed to4C, the frequency will be [2006]
The primary and secondary coil of a transformerhave 50 and 1500 turns respectively. If themagnetic flux φ linked with the primary coil isgiven by φ= φ_{0} + 4t, where φ is in webers, t is timein seconds and φ_{0} is a constant, the outputvoltage across the secondary coil is [2007]
A transformer is used to light a 100 W and 110 Vlamp from a 220 V mains. If the main current is 0.5amp, the efficiency of the transformer isapproximately [2007]
What is the value of inductance L for which the current is maximum in a series LCR circuit with C = 10 μF and ω = 1000s ^{1} ? [2007]
In an a.c circuit the e.m.f. (e) and the current (i) at any instant are given respectively by
e = E_{0} sin ωt [2008]
i = I_{0} sin (ωt –φ)
The average power in the circuit over one cycle of a.c. is
Power dissipated in an LCR series circuit connected to an a.c source of emf εε is [2009]
In the given circuit the reading of voltmeter V_{1} and V_{2} are 300 volts each. The reading of the voltmeter V_{3} and ammeter A are
respectively [2010]
A 220 volts input is supplied to a transformer.The output circuit draws a current of 2.0 ampereat 440 volts. If the efficiency of the transformeris 80%, the current drawn by the primarywindings of the transformer is [2010]
An ac voltage is applied to a resistance R and aninductor L in series. If R and the inductivereactance are both equal to 3Ω, the phasedifference between the applied voltage and thecurrent in the circuit is [2011]
In an ac circuit an alternating voltage e = 200 √2 sin 100 t volts is connected to a capacitorof capacity 1μF. The r.m.s. value of the currentin the circuit is [2011]
The r.m.s. value of potential difference V shown in the figure is [2011M]
A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an ac source, of 200 volt, 100 Hz, is connected across the coil, the current in the coil will be [2011M]
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