List of top Physics Questions

An arc lamp requires a direct current of $10\, A$ at $80 \,V$ to function. If it is connected to a $220 \,V \,(rms)$, $50 \,Hz\, AC$ supply, the series inductor needed for it to work is close to :

Identify the semiconductor devices whose characteristics are given below, in the order $(a), (b), (c), (d)$ :

Two identical wires $A$ and $B$, each of length $l$, carry the same current $I$. Wire $A$ is bent into a circle of radius $R$ and wire $B$ is bent to form a square of side $a$. If $B_A$ and $B_B$ are the values of magnetic field at the centres of the circle and square respectively, then the ratio $\frac{B_A}{B_B}$ is :

In the shown arrangement of the meter bridge AC corresponding to null deflection of galvanometer is x. What would be its value if the radius of the wire AB is doubled?

Block A of mass m and block B of mass 2m are placed on a fixed triangular wedge by means of a massless, inextensible string and a frictionless pulley as shown in the figure. The wedge is inclined at 45° to the horizontal on both sides. If the coefficient of friction between block A and the wedge is (2)/(3) and that between block B and the wedge is (1)/(3), and both blocks A and B are released from rest, the acceleration of A will be:

The surface charge density of a thin charged disc of radius $ R $ is $ \sigma $. The value of the electric field at the centre of the disc is $ \dfrac{\sigma}{2\varepsilon_0} $. With respect to the field at the centre, the electric field along the axis at a distance $ R $ from the centre of the disc is:

The molecules of a given mass of a gas have an r.m.s. velocity of 200 m s⁻¹ at 27°C and 1.0 × 10⁵ N m⁻² pressure. When the temperature and pressure of the gas are 127°C and 0.05 × 10⁵ N m⁻², respectively, the r.m.s. velocity of its molecules is:

The approximate depth of an ocean is 2700 m. The compressibility of water is $ 45.4 \times 10^{-11} \, \text{Pa}^{-1} $ and the density of water is $ 10^3 \, \text{kg m}^{-3} $. What fractional compression of water will be obtained at the bottom of the ocean?

The mass of $ ^{15}\text{N} $ is 15.00011 amu and that of $ ^{16}\text{O} $ is 15.99492 amu. The mass of a proton is 1.00783 amu. Determine the binding energy of the last proton of $ ^{16}\text{O} $.

The frequency of vibration of a string is given by
$ \nu = \dfrac{p}{2l}\left(\dfrac{F}{m}\right)^{1/2} $
Here, $ p $ is the number of segments in the string and $ l $ is the length. The dimensional formula for $ m $ will be:

Two resistances at 0°C with temperature coefficients of resistance alpha₁ and alpha₂ joined in series act as a single resistance in a circuit. The temperature coefficient of their single resistance will be:

Two identical charged spheres suspended from a common point by two massless strings of length l are initially at a distance d ≪ l apart because of their mutual repulsion. The charges begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity v. Then v varies as a function of distance x between the spheres as:

A circular disc of radius R and thickness (R)/(6) has moment of inertia I about an axis passing through its centre perpendicular to its plane. It is melted and recast into a solid sphere. The moment of inertia of the sphere about its diameter is:

A resistor of resistance R, capacitor of capacitance C and inductor of inductance L are connected in parallel to an AC power source of voltage $ \varepsilon_0 \sin \omega t $. The maximum current through the resistance is half of the maximum current through the power source. Then value of R is:

Answer:
$ R = \sqrt{3}\left| \dfrac{1}{\omega C} - \omega L \right| $

The average kinetic energy of an ideal gas molecule in SI units at 25°C will be:

An inductor of inductance L = 400mH and resistors of resistance R₁ = 2Ω and R₂ = 2Ω are connected to a battery of emf 12V as shown in the figure. The internal resistance of the battery is negligible. The switch S is closed at t = 0. The potential drop across L as a function of time is:

In the figure below, what is the potential difference between the points A and B and between B and C respectively in steady state?

A frictionless wire AB is fixed on a sphere of radius R. A very small spherical ball slips on this wire. The time taken by this ball to slip from A to B is:

In the circuit shown in the figure, find the current in the 45Ω resistor.

A ray of light of intensity I is incident on a parallel glass slab at point A as shown in the diagram. It undergoes partial reflection and refraction. At each reflection, 25% of incident energy is reflected. The rays AB and A'B' undergo interference. The ratio of Imax and Imin is:

A wire carrying current I has the shape as shown in the adjoining figure. Linear parts of the wire are very long and parallel to X–axis while the semicircular portion of radius R lies in the Y-Z plane. Magnetic field at point O is:

A parallel plate capacitor of area A and plate separation d is filled with two dielectrics as shown. What is the capacitance of the arrangement?

A 1kg mass is attached to a spring of force constant 600N m⁻1 and rests on a smooth horizontal surface with other end of the spring tied to a wall as shown in the figure. A second mass of 0.5kg slides along the surface with initial speed 3m s⁻1. If the masses make a perfectly inelastic collision, then find the amplitude and time period of oscillation of the combined mass.

A source of sound S emitting waves of frequency 100Hz and an observer O are located at some distance from each other. The source is moving with a speed of 19.4m s⁻1 at an angle of 60^∘ with the source–observer line as shown. The observer is at rest. The apparent frequency observed is (velocity of sound in air =330m s⁻1):

A lens having focal length f and aperture of diameter d forms an image of intensity I. Aperture of diameter d/2 in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively: