NEB Class 12 Physics Most Important Question Chapterwise

Checkout XII Physics Most Important Short Question

Mechanics

Rotational Motion:

1. Define moment of inertia. Derive an expression for the moment of inertia of thin uniform rod about an axis through its center and perpendicular to its length.
2. Derive a relation between the torque and angular acceleration in case of a rigid body.
3. State the conservation of angular momentum. Derive the relation between torque and angular momentum.
4. Write the physical significance of moment of inertia. Show that $K.E = \frac{1}{2}I{\omega ^2}$ where the symbols have their usual meanings.

Simple Harmonic Motion:

1. Define simple harmonic motion. Show that the bob of a simple pendulum may move with simple harmonic motion and find its time period.
2. Find an expression for the energy of particle in SHM and show that the particle obeys the law of conservation of energy.

Fluid Statics

1. On what factors do the rise and fall of the liquid on the capillary tube depend on? Show that $T = \frac{{h\rho gr}}{{2{\mathop{\rm Cos}\nolimits} \theta }}$ where the symbols have their usual meanings.
2. Show that the surface tension is numerically equal to the surface energy of a liquid.
3. State and prove Bernoulli's theorem.

Heat and Thermodynamics

First Law of Thermodynamics

1. Define thermodynamic process. Derive an equation of state for an adiabatic process.
2. Why is C_p greater than C_v in a gas. Derive the relation between them.

Second Law of Thermodynamics:

1. Describe the working of Carnot engine with the help of P-V diagram.

Wave and Optics

Wave Motion:

1. Define wave motion. Derive the progressive wave equations in a medium.
2. Starting with the definition of stationary waves, prove that the distance between any two consecutive nodes or antinodes in a stationary wave is $\frac{\lambda }{2}$.

Mechanical Wave:

1. Write an expression for the Newton's formula for the velocity of sound in air. Explain the necessary correction made by Laplace.

Waves in Pipe and Strings:

1. Define end correction. Show that, in open organ pipe, both odd and even harmonics can be produced.
Define natural frequency. Describe an experiment to determine the velocity of sound in air by resonance air column tube method.

Acoustic Phenomena

1. Describe sound wave as a pressure wave and deduce an expression for the pressure amplitude.
2. What is Doppler effect in sound? Obtain an expression for the apparent frequency of sound when both source and observer are moving towards each other.

Nature of Propagation of Light:

1. State Huygens’s law and use it to verify Snell's law.

Interference:

1. Define coherent sources of light. Describe Young's double slit experiment and show that the bright fringes and dark fringes are equally spaced.

Diffraction

1. Define diffraction of light. Describe the diffraction of light at a single slit and find the condition for secondary maxima and minima.

Polarization:

1. Define polarization of light. Show that, $\mu = \tan {\theta _p}$, where the symbols have their usual meanings.

Electricity and Magnetism

Electric Circuit

1. How can you convert a galvanometer into ammeter (or voltmeter)? Explain.
2. State and apply Kirchhoff’s rule to measure the unknown resistance of a wire by using Wheatstone bridge circuit.
3. State the principle of meter bridge. Describe how it is used to determine the resistance of a wire.
4. What is the principle of potentiometer? Explain with necessary theory how you would determine the internal resistance of the internal resistance of a cell using this principle.

Thermo-electric Effect

1. What do you mean by thermos-electric effect? Discuss the variation of thermos-emf in a thermos-couple with the change in temperature.

Magnetic Field

1. State and explain Biot- Savart's law. Use it to find the magnetic field due to a long straight current carrying conductor or solenoid or current carrying circular coil.
2. State Ampere's law. Deduce an expression for the force between two parallel current carrying wires.

Magnetic properties of Materials:

1. What is meant by magnetic hysteresis are typical hysteresis curve and explain what can be deduced from this about magnetic properties of a material.

Electromagnetic Induction:

1. State Faraday's law of electromagnetic induction. Derive an expression for the emf induced in a straight conductor moving at right angles to the direction of a uniform magnetic field.
2. State Faraday's law of electromagnetic induction. Deduce an expression for the emf induced in a coil rotating uniformly in a uniform magnetic field.
3. Explain the principle and working of a transformer.

Alternating Current

1. Discuss the condition for resonant frequency of LCR alternating current circuit.
2. Derive an expression for the impedance of a LCR series a.c. circuit. Show graphically how impedance varies with the variation of applied frequency.

Modern Physics

Electron:

1. Describe about construction and working principle of Millikan's oil drop experiment to determine the charge of an electron.
2. Define cross field. Describe construction and working principle of J.J. Thomson's experiment to determine specific charge of an electron.

Photons:

1. Define threshold frequency and work function of a metal. Explain Einstein's photoelectric equation.
2. Describe the experiment to determine the Planck's constant.

Quantization of Energy:

1. State Bohr's postulates for atomic model. Derive the expression for radius of an electron bound to hydrogen atom . (OR, to find the total energy of an electron in nth orbit.)
2. Explain Bragg's law of diffraction for X - rays.

Radioactivity and Nuclear Reaction:

1. State the laws of radioactivity. Derive the relation between half-life period and decay constant.

---