CBSE Class 12 (Science) Alternating Current — practice questions
81 free MCQs with worked solutions. Tap any question for the answer + explanation, or practice them all in the app.
Practice CBSE Class 12 (Science) Alternating Current in the app →The effective value of an alternating current is called its:The household line voltage of 220 V is which kind of value?An inductor in an ac circuit offers:A capacitor in an ac circuit offers:The SI unit of reactance is the:The total opposition of an ac circuit is called its:Alternating voltages are stepped up or down by means of:The rms current equals the dc current that would produce the same:At resonance in a series LCR circuit, the impedance is:At resonance the current amplitude in the circuit is:Besides an inductor, resonance needs the circuit to contain a:The quantity cos of the phase angle is called the:A current that dissipates no power is referred to as:Maximum power is dissipated in a series LCR circuit at:Inductive reactance is directly proportional to the:At the resonant frequency, the two reactances are:A radio is tuned to a station by matching the resonant frequency of:Resonance is described as a phenomenon that is:The impedance of a series LCR circuit at resonance equals:A lagging wattless current is neutralised by adding an equal:Why is ac preferred over dc for distributing electrical energy?The mains supply in homes varies with time like which function?Ohm's law for a pure resistor holds for which kind of source?What is the phase difference between voltage and current in a pure resistor?What is the average value of a sinusoidal ac over one complete cycle?An ac has zero average, yet it heats a resistor. Why?An alternating current has a peak value of 10 A. What is its rms value?A household line labelled 220 V rms has roughly what peak voltage?A bulb rated 100 W on a 220 V supply has what hot resistance?What rms current does a 100 W bulb draw from a 220 V supply?The rms value of an alternating current equals which steady dc?In ac circuit analysis, what is a phasor?In a purely inductive ac circuit, how does current compare with voltage?In a purely capacitive ac circuit, the current isIf the source frequency is tripled, the reactance of an ideal inductorWhen the source frequency is doubled, capacitive reactance becomesA capacitor is fully charged by a dc source. What current flows afterwards?A lamp is in series with a capacitor. When does the lamp glow?A lamp in series with a capacitor runs on ac mains. If C is reduced, the lampA 15.0 microfarad capacitor is on a 220 V, 50 Hz supply. Peak current?A capacitor is connected to an ac source whose frequency is then doubled. The rms currentWhat is the reactance of a pure 25.0 mH inductor at 50 Hz?A pure 25.0 mH inductor is on a 220 V, 50 Hz supply. The rms current is aboutAn iron rod is pushed into a coil in series with a bulb on ac. The bulb glowWhat is the average power absorbed by a pure inductor over one full cycle?In a series LCR circuit, which quantity is the same in R, L and C at every instant?A series circuit has R = 3 ohm, XL = 8 ohm and XC = 4 ohm. Find its impedance.A 283 V peak source drives R = 3 ohm, XL = 8 ohm, XC = 4 ohm in series. Power dissipated?A coil has resistance 6 ohm and reactance 8 ohm in series. Its power factor isA 200 ohm resistor is in series with a capacitor of reactance 212 ohm. Impedance?A 200 ohm resistor and a 212.3 ohm reactance are in series on 220 V. rms current?In a series LCR circuit with XC greater than XL, the circuit behaves asA series LCR circuit with XC less than XL is predominantlyA series circuit has L = 1.00 mH and C = 1.00 nF. What is its resonant angular frequency?A series LCR circuit has R = 100 ohm and a 10 V peak source. Peak current at resonance?How is a radio tuned to one particular station?A driven oscillating system has a large amplitude when the driving frequency is near itsOn which principle does an airport metal detector work?Average ac power equals Vrms times Irms times which factor?What is the power factor of a circuit containing only an ideal capacitor?What name is given to the current in a purely inductive circuit that dissipates no power?Why is a low power factor undesirable in power transmission?R = 3 ohm, 200 V rms source, circuit at resonance. Power dissipated?On what principle does a transformer work?On what kind of core are transformer coils usually wound?A transformer whose secondary has more turns than its primary is calledAn ideal transformer has 100 primary and 200 secondary turns, input 220 V, 10 A. Secondary current?A transformer has 100 primary turns, 200 secondary turns and a 220 V input. Output voltage?A transformer steps 2200 V down to 220 V. The primary has 1000 turns. Secondary turns?An ideal transformer takes 5 A at 220 V. Its 110 V secondary delivers what current?How can flux leakage in a transformer be reduced?Which transformer loss is the heating of the windings due to their resistance?Which core construction reduces eddy current loss in a transformer?Why is voltage stepped up before long-distance power transmission?A mains rating of 240 V refers to which type of value?The power rating printed on an ac appliance refers to itsHow does the frequency of a transformer's secondary output compare with the input?An ac voltage has a peak value of 340 V. Its rms value is aboutAn ac ammeter reads 2.0 A. What is the peak current in the wire?Most electric power in the world is generated at which frequencies?At very high frequency, where does ac concentrate in a wire?