List of top Physics Questions

The half-life of a radioactive substance is 20 minutes. $\frac{1}{3}$rd part of substance has decayed in time $t_1$ and $\frac{2}{3}$rd part of it has decayed in time $t_2$. Then, ($t_2 - t_1$) is nearly

An amplitude modulated wave is represented by $C_m(t) = 30 \sin 300\pi t + 10(\cos 200\pi t - \cos 400\pi t)$. Then the carrier wave frequency, signal frequency and modulation index are respectively

In photo electric experiment, if the wavelength of incident light on the metal changes from 200 nm to 300 nm. The decrease in stopping potential is about ($\frac{hc}{e} = 1240$ eV - nm)

In the pfund series of hydrogen spectrum, the wavelength of first spectral line is (Rydberg constant = 1.097 $\times 10^7$ m$^{-1}$)

The following circuit represents the logic gate

The coefficient of mutual induction between the primary and secondary coil of a transformer is $0.4\text{ H}$. When the current in the primary coil changes at the rate of $10\text{ As}^{-1}$, then the induced emf in the secondary will be:

The equitorial magnetic field of earth on its surface at equator is $0.4\text{ G}$. Then its dipole moment is (The radius of the earth $R=6400\text{ km}$):

Two long parallel straight conductors separated by $10\text{ cm}$ carrying currents $20\text{ A}$, $40\text{ A}$ in the same direction. The work required per unit length to move the conductors apart to $30\text{ cm}$ is [Take $\log_{10} 3 = 0.4771$]:

Match the following, if $X_{\text{L}}$ and $X_{\text{C}}$ are inductive and capacitive reactances respectively:

Magnetic field at $0.1\text{ m}$ from a long straight wire carrying $10\text{ A}$ current is:

Which one of the following laws is modified by Maxwell to obtain four electromagnetic equations known as Maxwell's equations?

A wire of length $1\text{ m}$ is broken into two unequal parts $P$ and $Q$. Part $P$ is extended to double its length so that its resistance become equal to resistance of $Q$. The length of $Q$ part is:

Work done in assembling two identical charges each having a charge 'q', separated by a distance $r$ is:

A parallel plate capacitor is charged and then disconnected from the battery. If a dielectric slab is now inserted between the plates of the capacitor, the energy stored in the capacitor:

Ten resistors, each having resistance of $6\text{ }\Omega$, are connected in a circuit. Then the ratio of maximum current to the minimum current that can flow through the circuit is:

The surface charge density of an isolated sphere A of radius $2\text{ cm}$ having a charge of $+10\text{ }\mu\text{C}$ is twice the surface charge density of another sphere B of radius $3\text{ cm}$. If the two spheres are joined and then separated, the charges on the sphere A and B after separation are respectively:

If the absolute temperature of the source of a Carnot's engine is changed from $T_1$ to $T_2$, its efficiency increases from $0.25$ to $0.4$. If the temperature of the sink is constant, then the ratio of $T_1$ and $T_2$ is:

A source of sound and an observer are moving each with a speed of $10\%$ of the speed of sound in air. If the frequency of sound heard by the observer when they approach each other is $400\text{ Hz}$ more than the frequency of sound heard by the observer when they move away from each other, then the frequency of the source of sound is:

When a light ray is incident on a small angle prism of material of refractive index 1.5, the angle of minimum deviation is $7^\circ$. If the prism is immersed in a liquid of refractive index 1.2, then the angle of minimum deviation is:

When light of wavelength $\lambda$ incidents on a single slit of width 'a', then the angular width between the third order diffraction maxima on either side of the central maximum is:

An object placed in front of a concave mirror at a distance of $x\text{ cm}$ from the pole gives a 3 times magnified real image. If it is moved to a distance of $(x + 5)\text{ cm}$, the magnification of the image becomes 2. The focal length of the mirror is:

The ratio of the degrees of freedom of a monoatomic gas and a nonlinear polyatomic gas having 2 vibrational modes is:

Two liquids $A$ and $B$ are at temperatures $40^\circ\text{C}$ and $20^\circ\text{C}$ respectively. When equal masses of these liquids are mixed, the temperature of the mixture is found to be $35^\circ\text{C}$. The ratio of specific heats of $A$ and $B$ is:

The workdone by a gas of one mole at constant temperature of $27^\circ\text{C}$ when its volume doubled is (Take $\log_{10} 2 = 0.3010$ and Universal gas constant $R = 8.314\text{ J mol}^{-1}\text{ K}^{-1}$):

A Celsius and a Fahrenheit thermometers are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers $131^\circ$. The fall in temperature as registered by the Celsius thermometer is: