List of top Physics Questions

Derive an expression for the torque acting on a rectangular current loop suspended in a uniform magnetic field.

A charged particle is moving in a circular path with velocity $ V $ in a uniform magnetic field $ \vec{B} $. It is made to pass through a sheet of lead and as a consequence, it looses one half of its kinetic energy without change in its direction. How will (1) the radius of its path change? (2) its time period of revolution change?

Two wires P and Q are made of the same material. Wire Q has twice the diameter and half the length of wire P. If the resistance of wire P is $ R $, the resistance of wire Q will be:

You are required to design an air-filled solenoid of inductance $ 0.016 \, \text{H} $ having a length $ 0.81 \, \text{m} $ and radius $ 0.02 \, \text{m} $. The number of turns in the solenoid should be:

A voltage $ v = v_0 \sin(\omega t) $ applied to a circuit drives a current $ i = i_0 \sin(\omega t + \varphi) $ in the circuit. The average power consumed in the circuit over a cycle is:

The given diagram exhibits the relationship between the wavelength of the electromagnetic waves and the energy of photons associated with them. The three points P, Q, and R marked on the diagram may correspond respectively to:

A beaker is filled with water (refractive index $ \frac{4}{3} $) up to a height $ H $. A coin is placed at its bottom. The depth of the coin, when viewed along the near normal direction, will be:

The stopping potential $ V_0 $ measured in a photoelectric experiment for a metal surface is plotted against frequency $ \nu $ of the incident radiation. Let $ m $ be the slope of the straight line so obtained. Then the value of the charge of an electron is given by $ h $ (where $ h $ is the Planck’s constant):

Let $ \lambda_e, \lambda_p, \lambda_d $ be the wavelengths associated with an electron, a proton, and a deuteron, all moving with the same speed. Then the correct relation between them is:

Which of the following figures correctly represent the shape of the curve of binding energy per nucleon as a function of mass number?

When a p-n junction diode is forward biased, the:

Assertion (A): It is difficult to move a magnet into a coil of large number of turns when the circuit of the coil is closed.

Reason (R): The direction of induced current in a coil with its circuit closed, due to motion of a magnet, is such that it opposes the cause.

Assertion (A): The deflection in a galvanometer is directly proportional to the current passing through it.

Reason (R): The coil of a galvanometer is suspended in a uniform radial magnetic field.

Assertion (A): We cannot form a p-n junction diode by taking a slab of a p-type semiconductor and physically joining it to another slab of an n-type semiconductor.

Reason (R): In a p-type semiconductor, $ n_e \gg n_h $ while in an n-type semiconductor $ n_h \gg n_e $.

Assertion (A): The potential energy of an electron revolving in any stationary orbit in a hydrogen atom is positive.
Reason (R): The total energy of a charged particle is always positive.

In a diffraction experiment, the slit is illuminated by light of wavelength 600 nm. The first minimum of the pattern falls at $ \theta = 30^\circ $. Calculate the width of the slit.

In a Young's double-slit experiment, two light waves, each of intensity $ I_0 $, interfere at a point, having a path difference $ \frac{\lambda}{8} $ on the screen. Find the intensity at this point.

Prove that, in the Bohr model of the hydrogen atom, the time period of revolution of an electron in the $ n $-th orbit is proportional to $ n^3 $.

A p-type Si semiconductor is made by doping an average of one dopant atom per $ 5 \times 10^7 $ silicon atoms. If the number density of silicon atoms in the specimen is $ 5 \times 10^{28} \, \text{atoms m}^{-3} $, find the number of holes created per cubic centimeter in the specimen due to doping. Also give one example of such dopants.

Two batteries of emf 3V 6V and internal resistances 0.2Ω 0.4Ω are connected in parallel. This combination is connected to a 4Ω resistor. Find:
(i) the equivalent emf of the combination
(ii) the equivalent internal resistance of the combination
(iii) the current drawn from the combination

A conductor of length $l$ is connected across an ideal cell of emf $E$.
Keeping the cell connected, the length of the conductor is increased to $2l$ by gradually stretching it.
If $R$ and $R'$ are the initial and final values of resistance, and $v_d$ and $v_d'$ are the initial and final values of drift velocity, find the relation between:
(i) $R'$ and $R$
(ii) $v_d'$ and $v_d$

When electrons drift in a conductor from lower to higher potential, does it mean that all the ’free electrons’ of the conductor are moving inthe same direction?

Using Biot-Savart law, derive expression for the magnetic field $ \vec{B} $ due to a circular current carrying loop at a point on its axis and hence at its center.

Show that the energy required to build up the current $ I $ in a coil of inductance $ L $ is $ \frac{1}{2} L I^2 $.

Considering the case of magnetic field produced by air-filled current carrying solenoid, show that the magnetic energy density of a magnetic field $ B $ is $ \frac{B^2}{2\mu_0} $.