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ISC Class 12 Physics Solved Question Paper 2012

Short Answer Type

21. Three point charges Q₁ = 25μ C, Q₂ = 50μ C, and Q₃ = 100μ C are kept at the comers A, B and C respectively of an equilateral triangle ABC having each side equal to 7.5 m. Calculate the total electrostatic potential energy of the system.

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22. Obtain and expression for equivalent capacitance C, when three capacitors having capacitance C₁ , C₂ and C₃ are connected in series.

Due to the applied p.d V,charge supplied by the battery is Q and due to induction,charge developed on each battery is Q applied p d are v₁ ,v₂ and v₃ .

V = V₁ + V₂ + V₃...(i)

Q = i₁V₁ = i₂V₂ = i₃V₃---(ii)

In place of the above arrangement a single capacitor C _equ is imagined which can withstand the applied P.D v and can store the same magnitude of charge Q.

Q =C_equV ---(iii)

From Eq. (i) + Eq. (iii)

Q = C_equ(V₁+V₂+V₃) ... (iv)

From Eq. (ii) + Eq. (iv)

$straight Q over straight C subscript eq space equals space Q over C subscript 1 space plus space Q over C subscript 2 space plus space Q over C subscript 3 Q over C subscript e q u i v. end subscript space equals space 1 over C subscript 1 space plus space 1 over C subscript 2 space plus space 1 over C subscript 3$

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23. When a potential difference of 3V is applied between the two ends of a 60 cm long metallic wire, current density in it is found to be 1 x 10 ^-7 Am ². Find conductivity of the material of the wire in SI system.

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24. In the circuit shown in Figure 4 below, E is a battery of emf 6V and internal resistance 1Ω. Find the reading of the ammeter A, if it has negligible resistance :

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25. With the help of a neatly drawn and lebelled diagram, obtain balancing condition of a Wheatstone bridge.

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26. State any two differences between Peltier effect and Joule effect.

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27.

Adjecent figure shows a point P near a long conductor XY carrying a current I. MN is a short current carrying conductor, kept at the point P, parallel to the conductor XY.

(i) What is the direction of magnetic flux density ‘B’ at the point P due to the current flowing through XY?

(ii) What is the direction of the force experienced by the conductor MN due to the current flowing through XY?

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28. What the four different types of energy losses in a transformer? State how to reduce/ minimize any one of them.

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29. A 50μ F capacitor, a 30 Ω resistor and a 0.7 H inductor are connected in series to an ac supply which generates an emf ‘e’ given by e = 300 Sin (200t) Volt. Calculate peak value of the current flowing through the circuit

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30. On the basis of Huygen’s wave theory, prove Snell’s law of refraction of light. Draw a neat and lebelled diagram. (Postulates of Huygen’s wave theory not required).

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