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ISC Class 12 Physics Solved Question Paper 2009

Short Answer Type

21.

(i) What is meant by:

(1) Drift velocity and

(2) Relaxation time?

(ii) A metallic plug AB is carrying a current I (see Figure 4 below). State how the drift velocity of free electrons varies, if at all, from end A to end B.

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22. Figure below shows a uniform manganin wire XY of length 100 cm and resistance 9 Ω, connected to an accumulator D of emf 4 V and internal resistance 1 Ω through a variable resistance R. E is sa cell of emf 1.8 V connected to the wire XY via a jockey J and a central zero galvanometer G. It is found that the galvanometer shows no deflection when XJ = 80 cm. Find the value of R.

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23. Obtain an expression for magnetic flux density ‘B’ at the center of a circular coil of radius R and having N turns, when a current I is flowing through it.

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24.
(i) State any two differences between a moving coil galvanometer and a tangent galvanometer.

(ii) What is the use of a Cyclotron?

(i) Differences between moving coil galvanometer and tangent galvanometer,

(ii) Cyclotron is particle accelerator. It is used to accelerate charged particles to high velocities by making them to pass repeatedly through the same accelerating region.

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25. What is meant by the time constant of an LR circuit? When the current flowing through a coil P decreases from 5A to 0 in 0.2 seconds, an emf of 60 V is induced across the terminals of an adjacent coil Q. Calculate the coefficient of mutual inductance of the two coils P and Q.

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26.

When an alternating emf e = 300 Sin (100 πt + π/6) Volt is applied to a circuit, the current I through it is I = 5.0 Sin (100 πt - π/6) ampere. Find the :

(i) Phase difference between the emf and the current.

(ii) Average power consumed by the circuit.

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27. Obtain an expression for resonant frequency ‘f₀’of a series LCR circuit.

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28.

In which part of the electromagnetic spectrum, do the following radiations lie:

(i) Having wavelength of 20 nm

(ii) Having frequency of 10 MHz

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29. A thin convex lens which is made of glass (refractive index 1.5) has a focal length of 20 cm. It is now completely immersed in a transparent liquid having refractive index 1.75. Find the new focal length of the lens.

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