Physics 12 past paper 2024

If the velocity of free electron is doubled, its De-Broglie wavelength changes by the factor of:

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What is meant by **'Magnetic Flux'** and **'Magnetic Flux density'**? Also give their units.

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State postulates of Bohr's atomic model. Show that energy of the electron in H-atom is quantized.

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Why energy dissipated per cycle (magnetization and demagnetization) for steel is more as compared to iron? Explain briefly.

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Derive an expression for charge to mass ratio (e/m) for an electron and then calculate its value.

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An expression for **current gain** of a transistor is given by:

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What is **Wien's displacement law**? Explain briefly.

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What is **photoelectric effect**? Why classical physics fails to explain photoelectric effect? Derive Einstein photoelectric equation.

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For an atom in excited state $n=5$, maximum number of transitions that take place is:

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Prove that $E = -\frac{\Delta V}{\Delta r}$.

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What is a potentiometer? Explain its principle, construction and working. Also give some uses.

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Differentiate between **controlled** and **uncontrolled nuclear chain reactions**. How is the chain reaction controlled?

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State and explain Gauss's law. Find electric field intensity between two oppositely charged parallel plates.

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In an RLC series circuit, the current at resonance frequency is:

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Why in a transistor the base region is made thin and lightly doped?

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Explain the phenomenon of self-inductance of a coil. What is its unit? On what factors does self-induction depend?

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Distinguish between **N-type semiconductor** and **P-type semiconductor**.

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What is an RLC series resonance circuit? Draw its impedance diagram. Also give its properties.

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The force acting on a charged particle kept between the plates of a charged capacitor is $F$. If one of the plates of the capacitor is removed, the force on the particle becomes:

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Calculate the longest wavelength of radiation for the Lyman series of hydrogen spectra.

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What is meant by **'half-life'** of a radio-active element? Show that $T_{1/2} = 0.693 / \lambda$.

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The best instrument for the accurate measurement of emf of a cell is:

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Differentiate 'Curie temperature' and 'Critical temperature'.

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The AC circuit in which current and voltage are in phase, the power factor is:

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How does a capacitor discharge ignition system work? Enlist some of its uses.

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The temperature below which the resistivity of a superconductor falls to zero is called:

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Briefly explain **resistivity**. How does it depend on temperature?

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How can a galvanometer be converted into a voltmeter? Draw a circuit diagram as well.

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Galvanometer is sensitive when the value of $\frac{C}{BAN}$ is:

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How are **eddy currents** produced? Identify their heating effects.

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With the increase in speed of motor, the magnitude of back emf:

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How does a Geiger-Müller counter detect and count radiation?

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If $\frac{N_s}{N_p} = 1$ then the transformer is:

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In a transformer, why is a laminated iron core used instead of a solid one?

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A wire is stretched to double of its length, its **strain** is:

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A coil having a resistance of $10\text{ Ohm}$ and an inductance of $32\text{ mH}$ is connected to $220\text{ V}, 50\text{ Hz}$ AC supply. Calculate current passing through the coil…

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What is meant by **peak value** and **effective value** of sinusoidal current? Give relation between them.

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Differentiate **Paramagnetic** and **Diamagnetic** materials with one example each.

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Briefly explain working of transistor as a switch.

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What is meant by **meta-stable state** and **population inversion** for LASER action?

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Calculate the **De Broglie wavelength** of an electron having $KE = 1200\text{ keV}$.

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Discuss the difference between **Hadrons** and **Leptons**.

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How much energy is released when $0.5\text{ kg}$ of $U^{235}$ undergoes fission reaction? (If the disintegration energy per event is $Q = 208\text{ MeV}$.)

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What is meant by **Alpha factor** and **Beta factor** for common emitter configuration of transistor? Derive relation between them.

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Briefly explain the principle of metal detector with circuit diagram.

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What is **electron volt (eV)**? Derive its relation with SI unit of energy.

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Under what condition a source (battery or cell) gives maximum power output? Discuss briefly.

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State **Lenz's law**. Prove that it is according to law of conservation of energy.

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