List of top Physics Questions

A force of 49 N acts tangentially at the highest point of a sphere (solid of mass 20 kg) kept on a rough horizontal plane. If the sphere rolls without slipping, then the acceleration of the center of the sphere is:
Two cells of emf 10 V each, two resistors of 20 \( \Omega \) and 10 \( \Omega \), and a bulb B of 10 \( \Omega \) resistance are connected together as shown in the figure. Find the current that flows through the bulb.
Two cells of emf 10 V each, two resistors
A metal sheet is inserted between the plates of a parallel plate capacitor of capacitance C. If the sheet partly occupies the space between the plates, the capacitance:

A battery of emf \( E \) and internal resistance \( r \) is connected to a rheostat. When a current of 2A is drawn from the battery, the potential difference across the rheostat is 5V. The potential difference becomes 4V when a current of 4A is drawn from the battery. Calculate the value of \( E \) and \( r \).

In an intrinsic semiconductor, carrier’s concentration is \( 5 \times 10^8 \ \text{m}^{-3} \). On doping with impurity atoms, the hole concentration becomes \( 8 \times 10^{12} \ \text{m}^{-3} \).

[(a)] Identify (i) the type of dopant and (ii) the extrinsic semiconductor so formed.

[(b)] Calculate the electron concentration in the extrinsic semiconductor.
Draw a plot of frequency \( \nu \) of incident radiations as a function of stopping potential \( V_0 \) for a given photoemissive material. What information can be obtained from the value of the intercept on the stopping potential axis?
In the given figure, three identical bulbs P, Q, and S are connected to a battery.
three identical bulbs P, Q, and S

[(i)] Compare the brightness of bulbs P and Q with that of bulb S when key K is closed.

[(ii)] Compare the brightness of the bulbs S and Q when the key K is opened.
Justify your answer in both cases.
A wire has a resistance of \( 10 \, \Omega \) at \( 20^\circ \text{C} \). If the temperature coefficient of resistance of the material is \( 0.004 \, \text{per}^\circ \text{C} \), what is the resistance of the wire at \( 50^\circ \text{C} \)?
In the circuit shown, assuming the threshold voltage of the diode is negligibly small, then the voltage \( V_{AB} \) is correctly represented by:
threshold voltage of the diode is negligibly small
A thin plano-concave lens with its curved face of radius of curvature R is made of glass of refractive index \( n_1 \). It is placed coaxially in contact with a thin equiconvex lens of same radius of curvature of refractive index \( n_2 \). Obtain the power of the combination lens.
The ends of six wires, each of resistance R (= 10 \(\Omega\)) are joined as shown in the figure. The points A and B of the arrangement are connected in a circuit. Find the value of the effective resistance offered by it to the circuit.
The ends of six wires, each of resistance
An electric dipole consists of charges \(\pm 4 \mu C\) separated by a distance of \(6\,cm\). Calculate the electric field at a point on the axial line at a distance \(20\,cm\) from its center.
A simple pendulum has a length of $ L = 2 \, \text{m} $. What is the time period of the pendulum? (Assume $ g = 9.8 \, \text{m/s}^2 $)
A projectile is launched with an initial velocity of \( 20 \, \text{m/s} \) at an angle of \( 30^\circ \) with the horizontal. What is the maximum height reached by the projectile? (Take \( g = 10 \, \text{m/s}^2 \))
Which of the following materials belongs to diathermanous substance?

The net current flowing in the given circuit is ___ A.

The net current flowing in the given circuit
In the figure, curved lines represent equipotential surfaces. A charge \( Q \) is moved along different paths A, B, C, and D. The work done on the charge will be maximum along the path:
curved lines represent equipotential surfaces
A ball is thrown vertically upward with a speed of 49 m/s. How long will it take to return to the thrower’s hand?

Show the refraction of light wave at a plane interface using Huygens' principle and prove Snell's law.

A body weighs 48 N on the surface of the earth. The gravitational force experienced by the body due to the earth at a height equal to one-third the radius of the earth from its surface is:
If an electron in the excited state falls to ground state, a photon of energy 5 eV is emitted, then the wavelength of the photon is nearly
A charge \( Q \) is distributed over two concentric hollow spheres of radii \( r \) and \( R \) (\( R>r \)) such that their surface charge densities are equal. Find: \begin{enumerate} \item the electric field, and \item the potential at their common center. \end{enumerate}
A body of mass 100 g is moving in a circular path of radius 2 m on a vertical plane as shown in the figure. The velocity of the body at point A is 10 m/s. The ratio of its kinetic energies at point B and C is: (Take acceleration due to gravity as 10 m/s\(^2\)) 
body of mass 100 g is moving in a circular path
Find the magnetic field at a point 5 cm away from a long straight wire carrying current \( I = 20\,A \).
A concave mirror has a focal length of 20 cm. An object is placed 60 cm in front of the mirror. Find the image distance.