List of top Physics Questions

The amplitude of electric field in an electromagnetic wave in free space is \( 1000 \, \text{Vm}^{-1} \). The amplitude of the magnetic field in this electromagnetic wave is:
A bar magnet is initially at right angles to a uniform magnetic field. The magnet is rotated till the torque acting on it becomes one-half of its initial value. The angle through which the bar magnet is rotated is:
An ammeter connected in series in an AC circuit reads \( 10 \, \text{A} \). The maximum value of current at any instant in the circuit is:

Which one out of the following materials is \(\textit{not}\) paramagnetic
 

Which of the following is an electrical conductor at room temperature?
The magnification produced by a spherical mirror is \( -2.0 \). The mirror used and the nature of the image formed will be:
A long straight wire is held vertically and carries a steady current in upward direction. The shape of magnetic field lines produced by the current-carrying wire are :

Assertion : In an ideal step-down transformer, the electrical energy is not lost.

Reason (R): In a step-down transformer, voltage decreases but the current increases.

When the resistance measured between p and n ends of a p-n junction diode is high, it can act as a/an:

Assertion : In a semiconductor diode, the thickness of the depletion layer is not fixed.

Reason (R): Thickness of depletion layer in a semiconductor device depends upon many factors such as biasing of the semiconductor.

The energy of an electron in a hydrogen atom in ground state is -13.6 eV. Its energy in an orbit corresponding to quantum number \( n \) is -0.544 eV. The value of \( n \) is:

The alternating current \( I \) in an inductor is observed to vary with time \( t \) as shown in the graph for a cycle.
 

alternating current I in an inductor

Which one of the following graphs is the correct representation of wave form of voltage \( V \) with time \( t \)?}

A diamagnetic substance is brought, one by one, near the north pole and the south pole of a bar magnet. It is:
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.
In a photoelectric experiment with a material of work function 2.1 eV, the stopping potential is found to be 2.5 V. The maximum kinetic energy of ejected photoelectrons is:
When a p-n junction diode is forward biased:
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 \( \eta_e \gg \eta_h \) while in an n-type semiconductor \( \eta_h \gg \eta_e \).
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.
X-rays are more harmful to human beings than ultraviolet radiations because X-rays:
A voltage \( v = v_0 \sin \omega t \) applied to a circuit drives a current \( i = i_0 \sin (\omega t + \phi) \) in the circuit. The average power consumed in the circuit over a cycle is:
An electron in Bohr model of hydrogen atom makes a transition from energy level \(-1.51 \, \text{eV}\) to \(-3.40 \, \text{eV}\). Calculate the change in the radius of its orbit. The radius of orbit of electron in its ground state is \(0.53 \, \text{\AA}\).

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

A small rigid spherical ball of mass \( M \) is dropped in a long vertical tube containing glycerine. The velocity of the ball becomes constant after some time. If the density of glycerine is half of the density of the ball, then the viscous force acting on the ball will be (consider \( g \) as acceleration due to gravity):
Two wires of the same material and the same radius have their lengths in the ratio 2:3. They are connected in parallel to a battery which supplies a current of 15 A. Find the current through the wires.
Two cities X and Y are connected by a regular bus service with a bus leaving in either direction every T min. A girl is driving scooty with a speed of 60 km/h in the direction X to Y. She notices that a bus goes past her every 30 minutes in the direction of her motion, and every 10 minutes in the opposite direction. Choose the correct option for the period T of the bus service and the speed (assumed constant) of the buses.