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ISC Class 12 Physics Solved Question Paper 2013

Multiple Choice Questions

11. The Biot Savart’s Law in vector form is:

$dB with rightwards harpoon with barb upwards on top space equals space fraction numerator mu subscript o over denominator 4 pi end fraction space fraction numerator d I space left parenthesis I with rightwards harpoon with barb upwards on top space x space r with rightwards harpoon with barb upwards on top right parenthesis over denominator r cubed end fraction$
$dB with rightwards harpoon with barb upwards on top space equals space fraction numerator mu subscript o over denominator 4 pi end fraction space fraction numerator straight I space left parenthesis dl with rightwards harpoon with barb upwards on top space x space r with rightwards harpoon with barb upwards on top right parenthesis over denominator r cubed end fraction$
$dB with rightwards harpoon with barb upwards on top space equals space fraction numerator mu subscript o over denominator 4 pi end fraction space fraction numerator straight I space left parenthesis straight r with rightwards harpoon with barb upwards on top space straight x space dl with rightwards harpoon with barb upwards on top right parenthesis over denominator r cubed end fraction$
$dB with rightwards harpoon with barb upwards on top space equals space fraction numerator mu subscript o over denominator 4 pi end fraction space fraction numerator straight I space left parenthesis straight r with rightwards harpoon with barb upwards on top space straight x space dl with rightwards harpoon with barb upwards on top right parenthesis over denominator r cubed end fraction$

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12.

In an astronomical telescope of refracting type :

Eyepiece has greater focal length.
Objective has greater focal length.
Objective and eyepiece have equal focal length.
Objective and eyepiece have equal focal length.

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13. The particles which cannot be accelerated by a cyclotron or a Van de Graff generator are :

Alpha particles
Beta particles
Neutrons
Neutrons

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Short Answer Type

14. A large hollow metallic sphere has a positive charge of 35.4μC at its centre. Find how much electric flux emanates from the sphere.

Charge, q = 35.4 μC = 35.4 x 10^-6 C

Therefore, Electric flux,

$straight ϕ space equals space straight q over straight epsilon subscript straight o space equals space fraction numerator 35.4 space straight x space 10 to the power of negative 6 end exponent over denominator 8.85 space cross times space 10 to the power of negative 12 end exponent end fraction space equals space 4 straight x 10 to the power of 6 space end exponent straight N space straight m squared space straight C to the power of negative 1 end exponent$

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15. A current T flows through a metallic wire of radius ‘r’ and the free electrons in it drift with a velocity v_d. Calculate the drift velocity of the free electrons through the wire of the same material, having double the radius, when same current flows through it.

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