List of practice Questions

The equation of AC voltage is \( E = 220 \sin(\omega t + \frac{\pi}{6}) \) and the AC current is \( I = 10 \sin(\omega t + \frac{\pi}{6}) \). The average power dissipated is

The current in an \( L-R \) circuit builds up to \( 3/4 \) of its steady state value in 4 seconds. The time constant of this circuit is

The magnetic flux in a closed circuit of resistance \(10 \, \Omega\) varies with time as \( \phi = (2t - 4t^2 + 1) \). The current in the loop will change its direction after a time of

Let the energy of an emitted photoelectron be \( E \) and the wavelength of incident light be \( \lambda_0 \). What will be the change in \( E \) if \( \lambda_0 \) is doubled?

A solid sphere of radius \( R \) carries a uniform volume charge density \( \rho \). The magnitude of electric field inside the sphere at a distance \( r \) from the centre is

Two point dipoles \( \mathbf{p_k} \) and \( \mathbf{L_k} \) are located at \( (0,0,0) \) and \( (1m, 0, 2m) \) respectively. The resultant electric field due to the two dipoles at the point \( (1m, 0, 0) \) is

An iron rod of length 2m and cross-sectional area of 50mm² stretched by 0.5mm, when a mass of 250 kg is hung from its lower end. Young’s modulus of iron rod is

Two resistances equal at \( 0^\circ \, \text{C} \) with temperature coefficient of resistance \( \alpha_1 \) and \( \alpha_2 \) joined in series

Current density varies with radial distance \( r \) as \( J = a r^2 \), in a cylindrical wire of radius \( R \). The current passing through the wire between radial distance \( R/3 \) and \( R/2 \) is

A potentiometer circuit shown in the figure is set up to measure emf of cell E. As the point P moves from X to Y, the galvanometer G shows deflection always in one direction, but the deflection decreases continuously until Y is reached. The balance point between X and Y may be obtained by

Two solenoids are given – 1st has 1 turn per unit length and 2nd has \(n\) turns per unit length. Ratio of magnetic fields at their centres is

Which statement is correct for the given circuit?

A positively charged particle is placed near an infinitely long straight conductor where there is zero gravity. Then

A metallic bar is heated from \(0^\circ \, \text{C}\) to \(100^\circ \, \text{C}\). The coefficient of linear expansion is \(10^{-5} \, \text{K}^{-1}\). What will be the percentage increase in length?

If the wavelength is brought down from 6000 Å to 4000 Å in a photoelectric experiment then what will happen?

For what value of \( A \), \( B \), and \( C \), the output \( Y = 1 \)?

If the terminal speed of a sphere of gold (density \(19.5 \, \text{g/cm}^3\)) is \(0.2 \, \text{m/s}\) in a viscous liquid (density \(1.5 \, \text{kg/m}^3\)), find the terminal speed of a sphere of silver (density \(10.5 \, \text{g/cm}^3\)) of the same size in the same liquid.

In shown fig, the circular loop of wire is moved with velocity towards the infinite current carrying wire. Then

For a current carrying inductor, emf associated is 20mV. Now, current through it changes from 6A to 2A in 2s. The coefficient of mutual inductance is

A square current carrying loop is changed to a circular loop in time \( t_1 \). Then

Holography is based on phenomenon of

In given circuit, all resistances are of \( 1 \, \Omega \). Current flowing through ammeter is

The wavelength of an electron for transition from a state \(n_1\) to \(n_2\) is \( \frac{9}{8R} \). Which of the following wavelengths is possible for a transition from \(n_2\) to \(n_1\)?

The potential energy of a system increases if work is done

In photoelectric effect, initially when energy of electrons emitted is \( E_0 \), de-Broglie wavelength associated with them is \( \lambda_0 \). Now, energy is doubled then associated de-Broglie wavelength \( \lambda' \) is