Physics-DPP-4-Electromagnetic Induction & Alternating current

PHYSICS Topic: E. M. I and A/C Date: 1. In the series LCR circuit, the voltmeter and ammeter readings are: (a) V = 100 volt, I = 2 amp (b) V = 100 volt, I = 5 amp (c) V = 1000 volt, I = 2 amp (d) V = 300 volt, I = 1 amp 2. In a step-up transformer, the turn ratio is 1 : 2. A leclanche cell (e.m.f. = 1.5 V) is connected across the primary. the voltage developed in the secondary would be: (a) 3.0 V (b) 0.75 V (c) 1.5 V (d) zero 3. A 40  electric heater is connected to a 200 V, 50 Hz main supply. The peak value of electric current flowing in the circuit is approximately: (a) 2.5 amp (b) 5.0 amp (c) 7.0 amp (d) 10 amp 4. The armature of DC motor has 20 resistance. It draws current of 2.5 ampere when run by 220 volt DC supply. The value of back e.m.f. induced in it will be: (a) 150 V (b) 170 V (c) 180 V (d) 190 V 5. A 10 ohm resistance, 5 mH coil and 10 F capacitor are joined in series. When a suitable frequency alternating current source is joined to the combination the circuit resonates. If the resistance is halved, the resonance frequency: (a) is halved (b) is doubled (c) remains unchanged (d) is quadrupled 6. A pure resistive circuit element X when connected to an AC supply of peak voltage 200 V gives a peak current of 5 A which is in phase with the voltage. Asecond circuit element Y, when connected to the same AC supply also gives the same value of peak current but the current lags behind by 90º. If the series combination of X and Y is connected to the same supply, what will be the rms value of current? 10 5 æç5ö÷ (a) amp (b) amp (c) ç ÷amp (d) 5amp 2 è2ø 7. The impedance of a circuit, when a resistance R and an inductor of inductance L are connected in series in an AC circuit of frequency f is: (a) (b) (c) (d) PHYSICS Topic: E. M. I and A/C Date: 8. The voltage of an AC supply varies with time (t) as V = 120 sin 100t cos 100t. The maximum voltage and frequency respectively are: (a) 60 volt, 100 Hz (b) 9. In a pure inductive circuit, current: π volt, 100 Hz (c) 120 volt, 100 Hz (d) 60 volt, 200 Hz. π (a) lags behind e.m.f. by 2 (b) leads the e.m.f. by 2 π (e) lags behind the e.m.f. by 4 (c) lags behind by  (d) leads the e.m.f. by  *****End of Paper***** PHYSICS Topic: E. M. I and A/C Answer key Date: 1. (a) 2. (d) 3. (c) 4. (b) 5. (c) 6. (c) 7. (c) 8. (a) 9. (a)

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