Physics 12 past paper 2025

Which of the following **CANNOT** be accelerated using electric field?

MCQ1 marksannual

By **Coulomb's law**, prove that the force between two point charges is reduced in a medium other than free space.

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Explain the concept of **Black body radiation** with the help of examples. Describe how energy is distributed over the wavelength range for different values of source temperature.…

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According to Quantum theory, increasing the brightness of a beam of light without changing the color will increase:

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Briefly illustrate the variation of binding energy per nucleon with the mass number. Also draw the graph.

Part B3 marksannual

What is an AC generator? How is an AC generator used to produce an alternating current? Explain with the help of a graph between instantaneous emf and time.

Part C7 marksannual

Primary function of transformer is to change:

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Write three postulates of Bohr's atomic model.

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Construct **phasor diagrams** and **impedance diagrams** of an R-L-C series circuit. Determine formula for impedance, phase angle and power factor.

Part C7 marksannual

A forward biased PN Junction offers:

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Differentiate 'statically induced emf' and 'dynamically induced emf'. Illustrate your answer with example.

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What is a mass spectrograph? Explain its working. Also show that the radius of the circular path of an isotope depends upon its mass.

Part C7 marksannual

Which is **NOT** the characteristic of LASER?

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Write three sources of emf by clearly specifying the energy conversion in each.

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Demonstrate **charging and discharging** of a capacitor through a resistance. Elaborate your answer with the help of Q-t graphs.

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If an electron and a proton have the same de-Broglie wavelength, which particle has greater speed? Justify.

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What are **X-rays**? How inner shell transitions in heavy elements result into emission of characteristic X-rays? Explain and draw diagrams.

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Compton effect proves the:

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When is **Compton shift** maximum? Prove it.

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State **Ampere's law**. Apply it to obtain a quantitative expression for the magnetic field inside a solenoid.

Part C6 marksannual

Which is an application of Mutual Induction?

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What is **rectification**? Describe the use of diodes for half and full wave rectification with circuit diagrams.

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The temperature at which a ferromagnetic material becomes paramagnetic is called:

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How can a galvanometer be converted into an ammeter? Draw diagram as well.

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SI unit of capacitive reactance is:

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A 300 kg load produces an extension 0.2 cm in a steel wire having length 2.0 m and cross-sectional area 15 cm². Determine: a) Stress, b) Strain, c) Young's Modulus for Steel (Y).

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What are the causes of power losses in a transformer? Write any three.

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Due to electric polarization of dielectric, the charge storing capacity of capacitor:

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A pure inductor is connected across a 10 V, 200 Hz AC supply and the current flowing through it is measured as 0.4 A. Determine the value of its inductance.

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What is meant by **magnetic flux**? State its unit.

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Which of the following series lies in the ultraviolet region?

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In which combination of capacitors the **energy stored** is maximum, parallel or series? Justify.

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Which one belongs to **Hadrons**?

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Calculate the longest and the shortest wavelengths for the Paschen series.

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Calculate the current through a single loop circuit if $\varepsilon = 120\text{ V}$, $R = 1000\text{ }\Omega$ and internal resistance $r = 0.01\text{ }\Omega$.

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A particle having the mass of an electron and charge of proton is called:

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Briefly describe the working of a rheostat as a potential divider circuit with diagram.

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Briefly describe the operation of an NPN transistor.

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Why is the **emitter-base junction** forward biased and the **collector-base junction** reverse biased?

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Distinguish between **emf** and **potential difference**. (Any three points)

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Briefly explain the role of **moderators** and **control rods** in nuclear reactor.

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What is **Coercivity**? Why is the coercive force of tungsten steel greater than that of iron?

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Briefly explain the **magnetic force** acting on a stationary charged particle placed in a uniform magnetic field.

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What are **superconductors**? Write down their four applications.

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In an **RL series circuit**, will the current lag or lead the voltage? Illustrate your answer by drawing waveforms and phasor diagrams.

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What is a Geiger-Müller counter? Briefly describe its working.

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Deduce the expression for maximum output power delivered to a load resistance.

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Write any three factors affecting the magnitude of the induced emf.

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