List of top Physics Questions

In the electric network shown, when no current flows through the $4\, \Omega$ resistor in the arm $EB$, the potential difference between the points $A$ and $D$ will be :

When $5\,V$ potential difference is applied across a wire of length $0.1\,m$, the drift speed of electrons is $2.5\times10^{-4}$ $ms^{-1}$. If the electron density in the wire is $8\times10^{28}\, m^{-3}$ the resistivity of the material is close to

The half life of a radioactive substance is $20\, minutes$. The time taken between $50\%$ decay and $87.5\%$ decay of the substance will be

A person is standing on a weighing-scale and observes that the reading is $60\,kg$ . He then suddenly jumps up and observes that reading goes to $70\,kg$ . Then his maximum upward acceleration is

Consider a spherical shell of radius $R$ at temperature $T$. The black body radiation inside it can be considered as an ideal gas of photons with internal energy per unit volume $u=\frac{U}{V} ? T^4$ and pressure $p=\frac{1}{3}\bigg(\frac{U}{V}\bigg)$ If the shell now undergoes an adiabatic expansion, the relation between $T$ and $R$ is

Consider an ideal gas confined in an isolated closed chamber. As the gas undergoes an adiabatic expansion, the average time of collision between molecules increases as $V^q$ , where $V$ is the volume of the gas. The value of $q$ is $\bigg(\gamma =\frac{C_p}{C_v}\bigg)$

A solid body of constant heat capacity $1 \, J/^{\circ}C$ is being heated by keeping it in contact with reservoirs in two ways (i) Sequentially keeping in contact with $2$ reservoirs such that each reservoir supplies same amount of heat. (ii) Sequentially keeping in contact with $8$ reservoirs such that each reservoir supplies same amount of heat. In both the cases, body is brought from initial temperature $100^{\circ}C$ to final temperature $200^{\circ}C$. Entropy change of the body in the two cases respectively, is

As an electron makes a transition from an excited state to the ground state of a hydrogen- like atom/ion

A long cylindrical shell carries positive surface charge $\sigma$ in the upper half and negative surface charge $-\sigma$ in the lower half. The electric field lines around the cylinder will look like figure given in: (figures are schematic and not drawn to scale)

A thin disc of radius $b\, = \,2a$ has a concentric hole of radius '$a$' in it (see figure). It carries uniform surface charge '$\sigma$' on it. If the electric field on its axis at height '$h$' $(h < < a)$ from its centre is given as '$Ch$' then value of '$C$' is :

Across a metallic conductor of non-uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is:

In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series is

The number of d-electrons in ${Fe^{2+} (Z=26)}$ is not equal to the number of electrons in which one of the following?

A short bar magnet is placed in the magnetic meridian of the earth with north pole pointing north. Neutral points are found at a distance of $30 \,cm$ from the magnet on the East - West line, drawn through the middle point of the magnet. The magnetic moment of the magnet in $Am^2$ is close to : (Given $\frac{\mu_{0}}{4\pi}=10^{-7}$ in SI units and $B_H$ = Horizontal component of earth's magnetic field = $3.6 \times 10^{-5}$ Tesla.)

A particle is executing a simple harmonic motion. Its maximum acceleration is $\alpha$ and maximum velocity is $\beta$ Then, its time period of vibration will be

Assuming human pupil to have a radius of $0.25\, cm$ and a comfortable viewing distance of $25\, cm$, the minimum separation between two objects that human eye can resolve at $500\, nm$ wavelength is

A direct current of $5\, A$ is superposed on an alternating current $I = 10 \,\sin \omega t$ flowing through the wire. The effective value of the resulting current will be

The cylindrical tube of a spray pump has radius $R$, one end of which has $n$ fine holes, each of radius $r$. If the speed of the liquid in the tube is $V$, the speed of the ejection of the liquid through the holes is

A glass capillary tube of internal radius $r=0.25\, mm$ is immersed in water. The top end of the tube projected by $2\, cm$ above the surface of the water. At what angle does the liquid meet the tube? Surface tension of water $=0.7\, N / m$.

If the capacitance of a nanocapacitor is measured in terms of a unit $'u'$ made by combining the electronic charge $V$, Bohr radius $'a_0'$, Planck's constant $'h'$ and speed of light $'c'$ then :

An $LCR$ circuit is equivalent to a damped pendulum. In an $LCR$ circuit the capacitor is charged to $Q _{0}$ and then connected to the $L$ and R as shown below :

R If a student plots graphs of the square of maximum charge $\left( Q _{\max }^{2}\right)$ on the capacitor with time $(t) $ for two different values $L_{1}$ and $L_{2}$ $\left(L_{1}>L_{2}\right)$ of $L$ then which of the following represents this graph correctly ? (Plots are shematic and not drawn to scale)

A particle is executing SHM along a straight line. It velocities at distances $x_1$ and $x_2$ mean position are $V_1$ and $V_2$, respecilvely. Its time period is :

4.0 g of a gas occupies 22.4 litres at NTP. The specific heat capacity of the gas at constant volume is 5.0 $JK^{-1} \, mol^{-1}$. If the speed of sound in this gas at NTP is 952 $ms^{-1}$, then the heat capacity at constant pressure is (Take gas constant R = 8.3 $JK^{-1} \, mol^{-1}$ )

Two identical thin plano-convex glass lenses (refractive index 1.5) each having radius of curvature of 20 cm are placed with their convex surfaces in contact at the centre. The intervening space is filled with oil of refractive index 1.7. The focal length of the combination is

Two vessels separately contain two ideal gases $A$ and $B$ at the same temperature, the pressure of $A$ being twice that of $B$. Under such conditions, the density of $A$ is found to be $1.5\, times$ the density of $B$. The ratio of molecular weight of $A$ and $B$ is :