Physics 12 past paper 2022

A point charge $+q$ is placed at the centre of a cube of side '$a$'. The electric flux emerging from the cube is:

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Explain why the capacitance of a parallel plate capacitor increases when a dielectric slab is placed between its plates?

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State the principle of an A.C generator. Explain by sketching a graph how an A.C generator is used to produce an alternating current.

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Why is it safe to stay inside an automobile during a light storm?

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Describe the process of charging and discharging of a capacitor by sketching the graphs for the growth and decay of charge on the capacitor.

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Is **E** necessarily zero inside a charged rubber balloon, if balloon is spherical? Assume that charge is distributed uniformly over the surface.

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A current carrying loop is placed in a magnetic field. Derive an expression for the torque acting on it.

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Two charges $5 \times 10^{-8}\text{ C}$ and $-3 \times 10^{-8}\text{ C}$ are located $16\text{ cm}$ apart. At what point on the line joining the two charges is electric potential z…

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State **Ampere's Law**. Derive an expression for the magnetic field due to a current carrying solenoid.

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A wire of uniform cross-sectional area '$A$' and length '$L$' is cut into two equal parts. The resistance of each part becomes:

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Why is the e.m.f of a cell always greater than its terminal voltage?

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Describe **hysteresis loop** for a magnetic material by drawing its curve for iron.

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Describe a circuit which will give a continuously varying potential.

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A long solenoid with $15\text{ turns per cm}$ has a small loop of area $2.0\text{ cm}^2$ placed inside the solenoid normal to its axis. If the current carried by the solenoid chang…

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The maximum output power is delivered to a load resistance '$R$', when the internal resistance '$r$' of the source is equal to:

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What is **Wheatstone bridge**? Deduce the condition for which Wheatstone bridge is balanced?

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Derive a relation for impedance and resonant frequency in an R.L.C series A.C circuit.

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State and prove **maximum power transfer theorem**.

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State the term **impedance** for an A.C circuit. Derive an expression for the impedance of R.L.C series A.C circuit. State the condition of resonance.

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The unit of magnetic flux density is:

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How can one separate particles of different velocities moving in a magnetic field?

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State **Gauss's law** for electrostatics. Using Gauss's Law, derive a relation for the electric field intensity at a point due to a uniformly charged infinite plane sheet.

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The unit of magnetic flux is:

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Will the two long, straight parallel wires carrying current in opposite direction attract or repel each other? Explain briefly.

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What are **X-rays**? Discuss how inner shell transitions in heavy elements result into emission of characteristic X-rays.

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Work done on a charged particle moving in a uniform magnetic field is:

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A copper wire of diameter $1.6 \text{ mm}$ carries a current of $20 \text{ A}$. Find maximum magnitude of magnetic field due to this current.

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The working principle of galvanometer is based upon:

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What is a galvanometer? How is a 5 mA, 100 Ω galvanometer converted into a 20 V voltmeter?

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When carrying electricity on long distances, step-up transformers are used to:

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How are **eddy currents** produced in an iron core of transformer and how can they be minimized?

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What is a **nuclear reactor**? Give the principle, construction and working of a typical nuclear reactor.

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If the motor is overloaded then the magnitude of back e.m.f:

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Can an efficient step up transformer increase the power level?

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State the photoelectric effect. Discuss experimental results and photon theory of the photoelectric effect.

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An induced e.m.f has no direction of its own. Explain briefly.

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State the postulates of special theory of relativity. Discuss time dilation and length contraction as a consequence of special theory of relativity.

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State and prove the second postulate of Bohr Model of Hydrogen atom.

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What is meant by **nuclear fusion**? Discuss how can energy be released in the fusion process? Illustrate with an example of proton-cycle.

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An electromagnetic wave is generated by:

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When an A.C source is connected to an ideal inductor, show that the average power supplied by the source over a complete cycle is zero.

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The phase difference between the current and voltage at resonance in R.L.C series A.C circuit is:

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Prove that an ideal capacitor connected to an A.C source does not dissipate power.

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If both the length and radius of the rod are doubled, then modulus of elasticity will:

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What is the basic principle of generation of electromagnetic waves?

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A body which breaks down just after crossing the elastic limit is known as:

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In an R.L series A.C circuit, will the current lag or lead the voltage? Illustrate your answer by a phasor diagram.

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Briefly explain the working principle of magnetic levitation train.

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Which factor does not affect the conductivity of a PN junction diode?

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Differentiate between **paramagnetic**, **diamagnetic** and **ferromagnetic** materials with suitable examples.

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In transistor, the emitter current $I_{E}$ is $3.5 \text{ A}$ and collector current $I_{C}$ is $2.35 \text{ A}$. What will be the base current?

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Why charge carriers are not present in the depletion region?

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Photon $A$ has twice the energy of photon $B$. What is the ratio of the momentum of $A$ to that of $B$?

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Draw and explain the stress-strain curve for a ductile material.

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How is a PN-junction diode used as a full-wave rectifier?

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Pair production occurs only when energy of photon is at least equal to:

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What is the working principle of magnetic levitation train? Explain how can it acquire high speed?

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If an object moves with speed of light, its mass will be:

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What is a transistor? Discuss the operation of NPN transistor.

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Which of the following series of hydrogen spectra lies in the ultraviolet region of the spectrum?

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Why is transistor called current amplification device?

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What is meant by **wave-particle duality**? Explain on the basis of de-Broglie hypothesis.

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Explain how a PN junction diode acts as a half wave rectifier?

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The process of generating three dimensional image of the object using laser beam is called:

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Calculate the shortest and longest wavelength of radiation for the Brackett Series.

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The quantity of uranium is $400\text{ g}$, the amount of uranium left after three half-lives is:

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Deduce the relation between $\alpha$ and $\beta$ of a transistor.

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Mass equivalent of $931 \text{ MeV}$ energy is:

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How can the spectrum of hydrogen contain so many lines even though a hydrogen atom has only a single electron?

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The particles that experience strong nuclear force are:

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The life time of electron in the excited state is about $10^{-8}\text{ s}$. What is the uncertainty in energy during this time?

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Describe the construction and working of Helium-Neon Laser.

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The mass of $^{14}_{7}N$ nucleus is $13.999234 \text{ u}$. Calculate its binding energy. Given that Mass of Proton $= 1.007276 \text{ u}$ and Mass of Neutron $= 1.008665 \text{ u}$…

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What factors make a fusion reaction difficult to achieve?

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How can energy be released in the nuclear fusion process?

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Find the energy released when $\beta$-decay changes $^{234}_{90}Th$ into $^{234}_{91}Pa$. Given that Mass of $^{234}_{90}Th = 234.0436u$, Mass of $^{234}_{91}Pa = 234.0428u$ and Ma…

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