Physics-DPP-3-Electromagnetic Induction & Alternating current

PHYSICS Topic: E. M. I and A/C Date: 1. A coil of resistance R and inductance L is connected to a battery of E volt e.m.f.. The final current flowing in the coil is: (a) E / R (b) E / L (c) E / (R2 + 2 L2)1/2 (d) EL / (R2 + L2)1/2 2. The potential difference V across and the current I flowing through an instrument in an AC circuit are given by: V = 5 cos t volt, I = 2 sin t volt The power dissipated in the instrument is: (a) zero watt (b) 5 watt (c) 10 watt (d) 2.5 watt 3. Power delivered by the source of circuit becomes maximum when: (a) L = C (b) ωL = 1 ωC (c) L = 1 – (1/C)2 (d) ωL = 4. L, C, R represent the physical quantities inductance, capacitance and resistance respectively. The combination which has the dimensions of frequency is: (a) (1 / RC) (b) (RL / C) (c) (R / LC) (d) (C / L) 5. If L, Q and R represent the inductance, charge and resistance respectively, then the units of: (a) (QR / L) will be of current (b) (Q2 R3 / L2) will be of energy (c) (QL / R) will be of current (d) (Q3 R2 / L) will be of power 6. An ideal coil of 10 henry is joined in series with a resistance of 5 ohm and a battery of 5 volt. Two seconds after joining, the current flowing in ampere in the circuit will be: (a) e–1 (b) (1 – e–1) (c) 1 – e (d) e 7. An inductor (L = 100 mH), a resistor (R = 100) and a battery (E = 100 volt) are initially connected in series as shown in the figure. After a long time, the battery is disconnected after short circuiting the points Aand B. The current in the circuit 1 ms after the short circuit is: (a) 1 amp (b) 1 amp e 8. Induced e.m.f. in the coil depends upon: (c) e amp (d) 0.1 amp (a) conductivity of the coil (b) amount of flux (c) rate of change of linked flux (d) resistance of coil 9. If coil is open, then L and R become: (a) , 0 (b) 0,  (c) ,  (d) 0, 0 10. An inductor L, a capacitor C and ammeters A1, A2 and A3 are connected to an oscillator in the circuit as shown in the adjoining figure. When the frequency of the oscillator is increased, then at resonant frequency, the ammeter reading is zero in the case of: (a) ammeter A1 (b) ammeter A2 (c) ammeter A3 (d) all the three ammeters *****End of Paper***** PHYSICS Topic: E. M. I and A/C Answer key Date: 1. (a) 2.(a) 3. (b) 4. (a) 5. (a) 6. (b) 7. (b) 8. (c) 9. (b) 10. (c)

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