List of top Physics Questions

A square shaped aluminium coin weighs 0.75 g and its diagonal measures 14 mm. It has equal amounts of positive and negative charges. Suppose those equal charges were concentrated in two charges (+Q and -Q) that are separated by a distance equal to the side of the coin, the dipole moment of the dipole is:
The electrostatic potential energy of the electron in an orbit of hydrogen is \( -6.8 \) eV. The speed of the electron in this orbit is (C is the speed of light in vacuum):
The current passing through a coil of 120 turns and inductance \( 40 \) mH is \( 30 \) mA. The magnetic flux linked with the coil is:
A thin uniform rod of length L and certain mass is kept on a frictionless horizontal table with a massless string of length L fixed to one end (top view is shown in the figure). The other end of the string is pivoted to a point O. If a horizontal impulse P is imparted to the rod at a distance x = L/n from the mid-point of the rod (see figure), then the rod and string revolve together around the point O, with the rod remaining aligned with the string. In such a case, the value of n is _____.
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The capacitance of a parallel plate capacitor is 400 pF. It is connected to an ac source of 100 V having an angular frequency 100 rad s$^{-1}$. If the rms value of the current is 4 μA, the displacement current is:
A 4 kg stone is attached to a steel wire being whirled at a constant speed of \( 12 \) m/s in a horizontal circle. The wire is 4 m long with a diameter of 2 mm, and Young’s modulus is \( 2 \times 10^{11} \) Nm\(^2\). The strain in the wire is:
For a $30^\circ$ prism, when a ray of light is incident at an angle $60^\circ$ on one of its faces, the emergent ray passes normal to the other surface. Then the refractive index of the prism is:
The relation between time \( t \) and displacement \( x \) is \( t = \alpha x^2 + \beta x \), where \(\alpha\) and \(\beta\) are constants. If \( \nu \) is the velocity, the retardation is:
The motion of a particle is given by \(X = a \cos t\), \(Y = a \sin t\) and \(Z = t\). The trajectory traced by the particle as a function of time is:
If \( S_1 \), \( S_2 \), and \( S_3 \) are the tensions at liquid-air, solid-air and solid-liquid interfaces respectively, and \( \theta \) is the angle of contact at the solid-liquid interface, then
A boy standing on a platform observes the frequency of a train horn as it passes by. The change in the frequency noticed as the train approaches and recedes from him with a velocity of 108 km/h (speed of sound in air = 330 m/s) is:
A conductor of length 1.5 m and area of cross-section \( 3 \times 10^{-5} \, \text{m}^2 \) has electrical resistance of 15 \( \Omega \). The current density in the conductor for an electric field of 21 \( \text{V/m} \) is.
A metal target with atomic number \( Z = 46 \) is bombarded with a high-energy electron beam. The emission of X-rays from the target is analyzed. The ratio \( r \) of the wavelengths of the \( K_\alpha \)-line and the cutoff is found to be \( r = 2 \). If the same electron beam bombards another metal target with \( Z = 41 \), the value of \( r \) will be:
The source of energy in the Sun is:
To generate energy, nuclear reactors use the principle of:
What back emf is induced in a coil of self-inductance 0.008 H when the current in the coil is changing at the rate of 110 A/s?
If a copper wire carries a current of 80.0 mA, how many electrons flow past a given cross-section of the wire in 10.0 minutes?
A parallel-plate capacitor has plates of dimensions 2.0 cm by 3.0 cm separated by a 1.0 mm thickness of paper. The relative dielectric constant of paper is 3.7. Find its capacitance.
A triode valve has an anode resistance of 20,000 and an amplification factor of 20. The mutual conductance is:
The deviation produced by an equilateral prism, when a ray of light is incident on it, does not depend on:

Complete the following nuclear equation: \( \^{30}_{15}Si + ? \rightarrow ? + 1e^0 \)

Two coherent monochromatic light beams of intensity \( I \) and \( 4I \) are superimposed. The maximum and minimum possible intensities in the resulting beam are:
A concave lens forms the image of an object which is:
Current \( I \) flows through a conducting wire of radius \( a \). The magnetic field \( B \) at a distance \( r \) from the centre of the wire (where \( r>a \) and \( \mu \) is the permeability of free space) is:
An electric bulb of volume 300 cm$^3$ was sealed off during manufacture at a pressure of 1 mm of mercury at 27°C. The number of air molecules contained in the bulb is, (R = 8.31 J mol$^{-1}$ K$^{-1}$ and $N_A = 6.02 \times 10^{23}$)