List of practice Questions

A long solenoid of radius R and length L has n turns per unit length. A circular loop of radius r(<R) is placed inside at the centre of the solenoid such that its axis coincides with the axis of the solenoid. Obtain the mutual inductance of the solenoid and the loop.
Two long straight parallel conductors A and B carrying steady currents $I_a$ and $I_b$ in the same direction are separated by a distance d. Deduce the expressions for the force acting on length L of conductor B due to conductor A and show it in figure. Write the expression for the force acting on length L of conductor A due to conductor B and show that it follows Newton's third law.
Calculate the de Broglie wavelength associated with an electron revolving in the second excited state of hydrogen atom. The ground state energy of the hydrogen atom is – 13.6 eV. Take $m_e = 9 \times 10^{-31}$ kg, $h = 6.6 \times 10^{-34}$ J.s.
Name the electromagnetic waves which are used as a diagnostic tool in medicine. Also write their wavelength range.
Name the electromagnetic waves which are used (ii) in remote switches for TV sets. Also write their wavelength range.
Assertion (A) : On forward biasing a p-n junction diode, the height of the barrier potential increases.
Reason (R) : In forward biasing of a p-n junction diode, the direction of the applied voltage is in the same direction as the built-in potential.
A 5 cm long pencil is placed along the principal axis of a concave mirror of focal length 20 cm such that its nearest end is at a distance of 25 cm from the mirror. Calculate the length of the image of the pencil.
In a Young’s double-slit experiment, a beam of light consisting of two wavelengths 500 nm and 600 nm is used. The interference fringes are observed at a screen placed 1.8 m away from the plane of slits (slit separation 0.3 mm). Calculate the least distance from the central maximum where the bright fringes due to both the wavelengths coincide.
Calculate the temperature at which the resistance of a conductor becomes 20% more than its resistance at $27^\circ\text{C}$. The value of the temperature coefficient of resistance of the material of conductor is $2.0 \times 10^{-4} ^\circ\text{C}^{-1}$.
A ray of light is incident on the face of a triangular prism of refracting angle $60^\circ$ and it just suffers total internal reflection at the other face. Find the angle of incidence for the ray if the refractive index of the material of the prism is $\sqrt{2}$.
Write two points of difference between intrinsic and extrinsic semiconductors.
A galvanometer of resistance $27 \Omega$ is converted into an ammeter of range (0 – 10 mA) using a resistance of $3 \Omega$. The galvanometer will show full scale deflection for a current of about –
The magnetic flux $\phi$ (in Wb) linked with a coil is related to time t (in s) as
$\phi = 5 At^2 + Bt - 2C$
The SI units of A and B are respectively
The figure shows the variation of capacitive reactance ($X_C$) of two ideal capacitors of capacitances $C_1$ & $C_2$ with the reciprocal of angular frequency ($1/\omega$) of ac source. The value of $C_1/C_2$ is
Assertion (A) : Light added to light can produce darkness.
Reason (R) : When two coherent light waves interfere, there is darkness at position of destructive interference.
Assertion (A) : Two electric heaters of power $P_1$ and $P_2$ ($> P_1$) are joined in series across a dc source of voltage V. The power consumed by the combination will be less than that consumed by $P_1$ when connected across the same source.
Reason (R) : The power consumed by a electric device when connected to a dc source of voltage V is proportional to its resistance.
Assertion (A) : On increasing the intensity of incident light of frequency $\nu$ ($> \nu_0$) on a photosensitive surface, the photocurrent increases.
Reason (R) : The stopping potential for a photosensitive surface increases with increase of frequency $\nu$ ($> \nu_0$) of incident light.
Two metal spheres of radii $r_1$ and $r_2$ ($> r_1$) having charges $q_1$ and $q_2$ respectively kept in air, are brought in contact. Which of the following statements is not correct ?
In Bohr model of hydrogen atom, an electron makes a transition from n = 4 state to n = 1 state and a photon of frequency $\nu$ is emitted. The frequency of photon emitted when an electron makes a transition from n = 4 state to n = 2 state in the same model is
Figure shows a magnet dropped through a small loop with a small cut. Which of the following statements is correct ?
The expression of magnetic fields associated with four electromagnetic waves are given below :
I. $B_1 = (4 \times 10^{-6} \text{ T}) \sin [0.7 \times 10^3 x + 1.4 \times 10^{11} t]$
II. $B_2 = (2 \times 10^{-7} \text{ T}) \sin [0.6 \times 10^3 x + 1.5 \times 10^{11} t]$
III. $B_3 = (3 \times 10^{-5} \text{ T}) \sin [0.5 \times 10^3 x + 1.5 \times 10^{11} t]$
IV. $B_4 = (5 \times 10^{-4} \text{ T}) \sin [0.2 \times 10^4 x + 4.8 \times 10^{11} t]$
Which wave is travelling in free space ?
Which of the following substance has relative magnetic permeability $\mu_r \gg 1$ ?
A straight conductor lies along x-axis and carries a current of 2 A along +x direction. The magnetic field at a point (0, 40 cm, 0) due to 1 cm length of conductor centered at the origin points along.
What is the difference between a ray and a wavefront ?
A plane wave is incident on a reflecting surface. Using Huygens principle, show how it is reflected from the surface. Hence, verify the law of reflection.