CBSE Physics E.M.I. and A.C. Expected Questions : Unit VI
[Short/V- Short Answer Questions-1, 2 Marks Each]
1. A vertical magnetic needle falls down through plane of magnetic meridian. Will any e.m.f. be produced between its ends ? Give reasons for your answer.
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2. Sketch a graph showing the variation of reactance of a capacitor with frequency of applied voltage.
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3. A small magnet is pivoted to move freely in the magnetic meridian. At what place on the earth’s surface will magnet be vertical ?
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4. A choke coil and a bulb are connected in series to a D.C. source. The bulb shines brightly. How does its brightness change when iron core is inserted in the choke coil ?
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5. Which device will you use to step up an a.c. voltage ? Can we use the same device to step up d.c. voltage ?
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6. The e.m.f. of an a.c. is given by the equation
E = 300 sin (314t) Write the values of heat voltage and frequency of the source.
7. What is the cause of E.M.I ?
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8. What is right hand rule ?
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9. Why are transformer are laminated ?
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10. What is dead beat galvometer ? How is this realised in practice ?
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11. Define henry
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12. How are coils of resistance box wound ?
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13. What are units of R/L and CR ?
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14. What is the rate of growth of current in LR circuit?
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15. Explain LC oscillations in terms of energy transfer.
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16. What leads E or I in a circuit containing an inductor ?
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17. What is the power consumed in a pure inductive circuit connected to a.c. ?
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18. What is the role of back e.m.f. in d.c. motor ?
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19. How energy losses in transformer be reduced ? Give two such steps.
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20. What is the main difference in d.c. dynamo and d.c. motor ? Can they be used for both purposes.
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21. What is resonance ?
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