List of top Physics Questions

Two light sources are said to be coherent if they are obtained from

Which of the following rays is emitted by a human body?

Zener diode is used for

For the current loops shown in the figure, Kirchhoff's loop rule for the loops $A H D C B A$ and AHDEFGA yields these equations respectively

For transistor action (1) Base, emitter and collector regions should have similar size and doping concentrations. (2) The base region must be very thin and lightly doped. (3) The emitter-base junction is forward biased and base-collector junction is reverse biased. (4) Both the emitter-base junction as well as the base-collector junction are forward biased. Which one of the following pairs of statements is correct?

$\upsilon_{1}$ is the frequency of the series limit of Lyman series, $\upsilon_{2}$ is the frequency of the first line of Lyman series and $\upsilon_{3}$ is the frequency of the series limit of the Balmer series. Then

A plano-convex lens is made of refractive index of $1.6 .$ The radius of curvature of the curved surface is $60\, cm$. The focal length of the lens is

Two thick wires and two thin wires, all of same material and same length, form a square in three different ways $P, Q$ and $R$ as shown in the figure. With correct connections shown, the magnetic field due to the current flow, at the centre of the loop will be zero in case of...........

A motorboat covers a given distance in $6$ hours moving downstream on a river. It covers the same distance in $10$ hours moving upstream. The time it takes to cover the same distance in still water is..........

There is a uniform magnetic field directed perpendicular and into the plane of the paper. An irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper. Then

A proton of mass $ 1.67 \times 10^{-27}\, kg$ enters a uniform magnetic field $1\, T$ of at point A shown in figure with a speed of $10^7\, ms^{-1}$ The magnetic field is directed normal to the plane of paper downwards. The proton emerges out of the magnetic field at point $C$, then the distance $AC$ and the value of angle $\theta $ will respectively be

A neutral water molecule $(H_2O)$ in its vapour state has an electric dipole moment of magnitude $6.4 \times 10^{-30} C-m$ . How far apart are the molecules centres of positive and negative charges?

A small coil is introduced between the poles of an electromagnet so that its axis coincides with the magnetic field direction. The number of turns is n and the cross-sectional area of the coil is $A$. When the coil turns through $180^{\circ}$ about its diameter, the charge flowing through the coil is $Q$. The total resistance of the circuit is $R$. What is the magnitude of the magnetic induction?

The ratio of the amounts of heat developed in the four arms of a balance Wheatstone bridge, when the arms have resistances $P = 100\, \Omega,\,Q = 10\, \Omega,\, R = 300\, \Omega$ and $S = 30\, \Omega$ respectively is

Sinusoidal carrier voltage of frequency $1.5\, MHz$ and amplitude $50\, V$ is amplitude modulated by sinusoidal voltage of frequency $10\, kHz$ producing $50 \%$ modulation. The lower and upper side-band frequencies in $kHz$ are

The collector plate in an experiment on photoelectric effect is kept vertically above the emitter plate. Light source is put on and a saturation photo-current is recorded. An electric field is switched on which has a vertically downward direction, then

The attenuation in optical fibre is mainly due to

In the hydrogen atom, the electron is making $6.6 \times 10^{15}$ rps. If the radius of orbit is $0.53 \times 10^{-10}$ m, then magnetic field produced at the centre of the orbit is

Hot water cools from $60^{\circ}C$ to $50^{\circ}C$ in the first $10$ minutes and to $42^{\circ}C$ in the next $10$ minutes. Then the temperature of the surroundings is

For detecting intensity of light we use

The Young's modulus of brass and steel are respectively $ 1.0\times 10^{11}Nm^{-2} $ and $ 2.0\times 10^{11}Nm^{-2}. $ .A brass wire and a steel wire of the same length are extended by $1 \,mm$ each under the same force. If radii of brass and steel wires are $R_B$ and $R_S$ respectively, then

The equivalent resistance across A and B is

The forbidden energy gap in $Ge$ is $0.72\, eV$. Given, $hc = 12400 \, eV \, - ?$ . The maximum wavelength of radiation that will generate an electron hole pair is

$\mu_0$ and $\varepsilon_0$ denote the permeability and permittivity of free space, the dimensions of $\mu_0 \varepsilon_0$ are

For any two vectors A and B, if $A\cdot B =|A \times B |$ , the magnitude of C = A + B is equal to