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ISC Class 12 Physics Solved Question Paper 2005

Short Answer Type

41.
Why are neutrons considered as ideal particles for nuclear fission reactions ? Calculate the energy released in the following nuclear reaction.

₁H²+ ₁H²→₂H⁴ +energy

(mass of 1H² = 2.014102 u, mass of ₂He⁴ = 4.002604 u).

Neutrons are used as projectiles in nuclear reaction, which initiates nuclear reactions and are present in product to carry the reaction further.

It is considered as ideal particles for nuclear reaction, because they are neutral particles on which neither any force of attraction nor any force of repulsion acts.

Mass of reactants = 2 x 2.014102 U = 4.028204 U

Mass of product = 4.002604 V

Mass defect = 4.028204 - 4.002604

Δm = 0.0256 U

Energy released = 0.0256 x 931 MeV

= 23.8336 MeV

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42. What is LED ? Explain how radiations are given out by LED.

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43. The output of a OR gate is connected to a NOT gate as shown in the figure given below. Name the new gate formed. Draw the logic symbol and truth table of the new gate.

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Long Answer Type

44. Two cells of same e.m.f. E, but different internal resistance r₁ and r₂ are connected to an external resistance R as shown in the figure. The voltmeter V reads zero. Obtain an expression for R in terms of r₁ and r₂. Calculate the voltage across the cell of internal resistance r₂. (Assume that the voltmeter V is of infinite resistance).

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45. In the figure given below, PQ is a long straight wire carrying a current of 5A in the direction of the arrow. An electron travels with a velocity of 10⁶ m/s at a distance 10 cm from the wire in the same direction of the current. Calculate the magnitude and direction of the force experienced by the electron.

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46. Explain with necessary formula (no derivation) how you will compare the magnetic moments of two magnets by equal distance method using a deflection magnetometer in tan A position.

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