CBSE Physics E.M.I. and A.C. Expected Questions : Unit VI
Derivation Type/Numericals (3-Marks Each)
1. A sinusiodal e.m.f. is applied to a circuit containing an inductor only. Show that the current lag behind voltage by n/2. A coil has an inductance of 1 henry, (a) At what frequency will it have reactance of 3,142Ω ? (b) What should be the capacity of the capacitor which has the same reactance at that frequency.
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2. Define mutual inductance. Write its S.I. units. Give two factors on which the coefficient of mutual inductance between pair of coils depends.
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3. Define the term self inductance. Write S.I unit. Give two factors on which self inductance of an air coil depends.
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4. A 28 turns coil with average diameter of 0.02 m is placed perpendicular to a magnetic field of 8,000 T. If the magnetic field changes for 3,000 T in 4s, what is the magnitude of the induced e.m.f. ?
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5. Prove that the total energy stored in an inductor is ½ LI2 max where I max is the maximum current
2 through the inductor.
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6. A capacitor of capacitane C is connected across an a.c. source of maximum e.m.f. Vo. What is the average power dissipated in the circuit ?
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7. State the Faraday’s law of electromagnetic induction.
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8. What os Lenz’s law ? Is it in accordance with law of conservation of energy ?
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9. What is Eddy or Focault’s current ? What are its advantages and disadvantages ?
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10. Derive an expression for the current at any instant in an a.c. circuit containing L and R.
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11. What are U-C oscillations ? How are these produced ?
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