List of top Physics Questions

State Gauss's theorem of electrostatics. What is the meaning of equipotential surface? Two insulator plates having equal charge density are placed as shown in the figure. Find the electric field intensity at points P and Q.
What are light emitting diodes? Describe the principle and working of a light emitting diode. Why are they more useful than traditional filament lamps?
What is the photoelectric effect? For any photosensitive surface threshold frequency is \( 3.3 \times 10^{14} \, \text{Hz} \). If frequency of incident light becomes \( 8.2 \times 10^{14} \, \text{Hz} \), then calculate the stopping potential and give the value of work function of the surface also.
Stating Huygens' principle of secondary wavelets, throw light on its success and failure. Draw the wavefront of light emerging from a convex lens due to a point source of light placed on its focus.
Give the relationship of temperature with the resistance and resistivity of a conductor. Define the temperature coefficient of the resistance and give its unit.
Explain the principle of potentiometer. Why is it superior to a voltmeter? How will you compare the e.m.f. of two cells by potentiometer? Explain by drawing a relevant circuit diagram.
Write lens maker's formula for a thin lens. On its basis, discuss the effect of refractive index of lens material and radius of curvature of lens surfaces on its focal length.
Write down the definition of coefficient of self-induction and coefficient of mutual induction. Current of 5 A decreases to zero in 0.1 s in a coil of 5 H self-inductance. Find out induced e.m.f. produced in the coil.
What is a transformer? Describe the energy losses occurring in a transformer.
Diameter of two spheres of metal are 6 cm and 4 cm. They are charged to the same potential. Find out the ratio of the surface densities of charge on the sphere.
How can the capacity of a conductor be increased? Radius of the plates of a parallel plate air capacitor is \( 3 \times 10^{-2} \, \text{m} \) and the capacitance is equal to the capacitance of a charged sphere of radius 1 m. Find the distance between the plates of the capacitor.
Draw a circuit diagram of a transistor amplifier in common emitter configuration and explain its working in brief.
Define electric dipole and dipole moment. An electric dipole of dipole moment \( 2 \times 10^{-8} \, \text{C} \cdot \text{m} \) is inclined at an angle of 30° from a uniform electric field of \( 2 \times 10^5 \, \text{V/m} \). Find the potential energy of the dipole and the moment of the couple acting on it.
The wavelength of light incident on a metal surface of work function 2.14 eV is 5000 \(\overset{\text{\small o}}{\text{A}}\). Find the maximum kinetic energy and the maximum velocity of the emitted photoelectrons.
Explain transverse nature of electromagnetic waves. Give a brief description of the uses of radio waves.
Equation of electric field of a plane electromagnetic wave is \( E_y = 60 \sin(500x - 1.5 \times 10^{11}t) \, \text{V/m} \). Write the equation for the magnetic field of the wave.
Write the formula for the momentum of a photon.
Draw symbol of NOR gate and draw truth table for its output.
Write down the difference between the chain reaction occurring in nuclear bombs and nuclear reactors.
What is meant by the binding energy of a nucleus? If mass defect for a nucleus is \( 10^{-6} \, \text{kg} \), then find its binding energy in electron volt.
Give the definition of isotopic and isobaric nuclei and mention the difference between them.
On the basis of Ampere's circuital law, find the expression for the magnetic field produced by an infinitely long straight current-carrying conductor.
Write down the phase difference between voltage and current in a pure inductive alternating circuit.
e.m.f. of a cell is 1.5 volt and internal resistance is \( 0.1 \, \Omega \). On connecting the cell with an external resistance of \( 2.9 \, \Omega \), what will be the potential difference at the terminals of the cell?
Angular momentum of electron in the second orbit of hydrogen atom is :