Physics-DPP1-7.Electromagnetic Induction & Alternating current

PHYSICS Topic: E. M. I and A/C Date: 1. Flux  (in weber) in a closed circuit of resistance 10 ohm varies with time t (in sec) according to the equation:  = 6t2 – 5t + 1. What is the magnitude of the induced current at t = 0.25 sec? (a) 1.2 A (b) 0.8 A (c) 0.6 A (d) 0.2 A 2. A magnet NS is suspended from a spring and while it oscillates the magnet moves in and out of the coil C. If the coil is now connected to a galvanometer G as shown in the figure, then as the magnet oscillates, G shows: (a) No deflection (b) Deflection on one side (c) Deflection to the leftand right with eonstant amplitude (d) Deflection to the left and right but amplitude steadily decreases 3. An electric potential difference will be induced between the ends of the conductor shown in the figure when the conductor moves in the direction: (a) P (b) Q (c) L (d) M 4. A conducting square loop of side L and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A magnetic induction B, constant in time and space, pointing perpendicular and into the plane of theloop exists everywhere. The current induced in the loop is: (a) Blv clockwise R (b) Blv anticlockwise R (c) 2Blv anticlockwise R (d) zero 5. Two different loops are concentric and lie in the same plane. The current in the outer loop is clockwise and increases with time. The induced current in the inner loop then is: (a) clockwise (b) zero (c) counterclockwise (d) in a direction that depends on the ratio of the loop radii PHYSICS Topic: E. M. I and A/C Date: 6. Aconductor rod AB moves parallel to x-axis in a uniform magnetic field, pointing in the positive x-direction. The end A of th rod gets: (a) Positively charged (b) negatively charged (c) neutral (d) first positively charged and then negatively charged 7. Figure shows a solenoid connected with a resistance R, a bulb B and a source of e.m.f. The resistance R is adjusted so that when the key K is closed, the bulb just glows. Then the switch K is suddenly opened. Then bulb B will: (a) remain as before (b) go out (c) glow very brightly (d) none of these 8. The north pole of a long horizontal bar magnet is being brought closer to a vertical conducting plane along the perpendicular direction. The direction of the induced current in the conducting plane will be: (a) horizontal (b) vertical (c) clockwise (d) anticlockwise 9. If the angular speed of rotation of an armature of alternating current generator is doubled, then the induced electromotive force will be: (a) twice (b) four times (c) no change (d) half 10. An aeroplane is moving towards north horizontally with a speed of 200 m s–1 at a place where the verticle component of earth’s magnetic field is 0.5 × 10–4 tesla. Then the induced e.m.f. set up between the tips of the wings of the plane if they are 10 m apart is: (a) 0.1 volt (b) 0.01 volt (c) 10 volt (d) 1 volt *****End of Paper***** PHYSICS Topic: E. M. I and A/C Answer key Date: 1.(d) 2.(d) 3. (d) 4. (d) 5. (c) 6. (b) 7. (c) 8. (b) 9. (a) 10. (a)

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