List of top Physics Questions

A wire of magnetic material of length \( 2L \) and magnetic moment \( M \) is bent at the centre to form 'L' shaped wire. Its magnetic moment is
A potentiometer wire is 4 m long and potential difference of 3 V is maintained between the ends. The e.m.f. of the cell which balances against a length of 100 cm of the potentiometer wire is
Surface density of charge on a charged conducting sphere of radius \( R \) in terms of electric intensity \( E \) at a distance \( r \) in free space is
\textit{(where \( r>R, \, \epsilon_0 \) is permittivity of free space)}
The work done in blowing a soap bubble of radius \(R\) is \(W_1\) at room temperature. Now, the soap solution is heated. From the heated solution another soap bubble of radius \(2R\) is blown and the work done is \(W_2\). Then
A capacitor is charged by a battery and energy stored is $U$. Now the battery is removed and the distance between plates is increased to four times. The energy stored becomes
An electron (\( e \)) is revolving in a circular orbit of radius \( r \) in a hydrogen atom. The angular momentum \( M \) of the electron is
\textit{(where \( M \) = magnetic dipole moment associated with it and \( m \) = mass of the electron)}
A circular coil of radius \( R \) is carrying a current \( I_1 \) in anticlockwise sense. A long straight wire is carrying current \( I_2 \) in the negative direction of x-axis. Both are placed in the same plane and the distance between the centre of coil and straight wire is \( d \). The magnetic field at the centre of coil will be zero for the value of \( d \) equal to
Moment of inertia of a solid sphere about its diameter is $I$. It is then cast into $27$ small spheres of same diameter. The moment of inertia of each new sphere is
Energy of the incident photon on the metal surface is ' 3W ' and then ' 5W ', where 'W' is the work function for that metal. The ratio of velocities of emitted photoelectrons is
A torque of 50 Nm acts on a body for 8 seconds which is initially at rest. The change in its angular momentum is
A body of mass \(m\) is moving along a circle of radius \(r\) with linear speed \(v\). Now, to change the linear speed to \(\dfrac{v}{2}\) and to move it along the circle of radius \(4r\), required change in the centripetal force of the body is
The non-zero potential difference across diode \(D_1\) and that across diode \(D_2\) are equal in the circuit shown in the figure (both diodes are identical in characteristics)
In conversion of moving coil galvanometer into an ammeter of required range, the resistance of ammeter so formed is
If the ratio of amplitudes of two sound waves is \(4:3\), then the ratio of maximum and minimum intensities is
When a beam of unpolarised monochromatic light is incident on a plane glass plate at a polarising angle, which one of the following statements is correct?
The angle made by a vector \( \vec{B} = 3\hat{i} + 2\hat{j} + 4\hat{k} \) with the y-axis is
A metal rod of Young’s modulus $Y$ and coefficient of linear expansion $\alpha$ has its temperature raised by $\Delta \theta$. The linear stress to prevent the expansion of rod is ($L$ and $\ell$ are original length of rod and expansion respectively)
One thousand small water drops of equal radii combine to form a big drop. The ratio of final surface energy to the total initial surface energy is
In a semiconductor, the number of holes and number of free electrons are represented as \( n_h \) and \( n_e \), respectively. Which one of the following statements is TRUE for the semiconductor?
How much energy is imparted to an electron so that its de-Broglie wavelength reduces from \( 10^{-10} \) m to \( 0.5 \times 10^{-10} \) m?
A particle executes linear S.H.M. with amplitude 4 cm. The magnitudes of velocity and acceleration are equal when it is 3 cm from the mean position. The time period of motion is
A block of mass \( m \) attached to one end of the vertical spring produces extension \( x \). If the block is pulled and released, the periodic time of oscillation is
A stone is tied at the end of a rope of length 1 m and whirled in a vertical circle. The ratio of velocity at the highest point to the lowest point will be
A bullet of mass $20\,\text{g}$ moving with a velocity of $200\,\text{m/s}$ strikes a target and is brought to rest in $\left(\dfrac{1}{50}\right)^{\text{th}}$ of a second. The impulse and average force of impact are respectively
Two masses \( M_1 \) and \( M_2 \) are accelerated uniformly on a frictionless surface as shown in figure. The ratio of the tensions \( \left( \frac{T_1}{T_2} \right) \) is