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ISC Class 12 Physics Solved Question Paper 2008

Short Answer Type

21. Obtain an expression for the electric potential at a point which is at a distance r from the point charge Q.

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22. Find the equivalent capacitance of the following circuit between the junctions A and B; given C₁ = C₂ = C₃ = C₄= 10μF and C₅ = 5,μF.

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23. A galvanometer with a coil of resistance 100 Cl and a scale having 100 divisions has a current sensitivity of 25 μ A / division.'How will you convert it into an ammeter of range 0 to 5A ?

Given,

G = 100 Ω , I = 5A

Current sensitivity - 25 μ A/division

No. of divisions = 100

∴ I_g = 25 x 10^-6 x 100 A

= 25 x 10^-4 A

In order to convert this galvanometer into an ammeter of range 0 - 5 A a suitable small resistance S has to be connected in parallel.

Therefore,

S space equals space fraction numerator straight I subscript straight g straight G over denominator straight I space minus space straight I subscript straight g end fraction space equals space fraction numerator 2.5 space x space 10 to the power of negative 4 end exponent space x space 100 space over denominator 5 space minus space 25 space x space 10 to the power of negative 4 end exponent end fraction space space space space space space space space space space space space space space space space space S space equals space fraction numerator 25 space x space 10 to the power of negative 2 end exponent over denominator 5 space minus space 0.0025 end fraction space space space space space space space space space space space space space space space space space S space equals space fraction numerator 25 space x space 10 to the power of negative 2 end exponent over denominator 4.9975 end fraction

S = 5.0025 x 10^-2

straight capital omega

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24. The emf ‘E’ of a thermocouple varies with the temperature θ (in degree C) of the hot junction (cold junction at 0°C) as E = 15 q 0.05 q^2.
Determine the neutral temperature.

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25. Using either deflection magnetometer or vibration magnetometer, explain how will you compare magnetic moments of two given bar magnets.

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26. Two very long straight parallel conductors carrying currents I₁ and I₂ in vacuum are separated by a distance ‘a’. Write an expression for the force experienced per unit length by one wire due to the current flowing through the other wire and hence define the fundamental unit of current, i.e., an ampere.

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27. When the primary of a transformer is connected to a 120 V AC mains, the current in the primary is 18.5 mA. Find the voltage across the secondary when it delivers 1.5 mA current through it, assuming the transformer to be an ideal one. State any one type of energy loss in a transformer.

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28. Draw a simple ray diagram showing the formation of a primary rainbow.

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29. Using Huygen’s Principle, prove the laws of refraction of light.

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30. The figure below shows the positions of the first bright fringes B₁, and B₂ on either side of the central bright fringe O in Young’s double slit experiment. Find the wavelength of monochromatic light used.