List of top Physics Questions

A cell in secondary circuit gives null deflection for \(2.5\,m\) length of wire for a potentialmeter having \(10\,m\) length of wire. If the length of the potentiometer wire is increased by \(1\,m\) without changing the cell in the primary, the position of the null point now is
The following series L-C-R circuit, when driven by an emf source of angular frequency \(70\) kilo-radians per second, the circuit effectively behaves like
Two radioactive materials \(x_1\) and \(x_2\) have decay constants \(10\lambda\) and \(\lambda\) respectively. Initially they have the same number of nuclei, then the ratio of the number of nuclei of \(x_1\) to that of \(x_2\) after a time \(t\) will be \(1/e\). The value of \(t\) is
A wire of length \(l\) is bent into a circular loop of radius \(R\) and carries a current \(I\). The magnetic field at the centre of the loop is \(B\). The same wire is now bent into a double loop of equal radii. If both loops carry the same current \(I\) and it is in the same direction, the magnetic field at the centre of the double loop will be
An infinitely long straight conductor is bent into the shape as shown below. It carries a current of \(1\) ampere and the radius of the circular loop is \(R\) metre. Then, the magnitude of magnetic induction at the centre of the circular loop is
A photon of energy \(E\) ejects a photoelectron from a metal surface whose work function is \(W_0\). If this electron enters into a uniform magnetic field of induction \(B\) in a direction perpendicular to the field and describes a circular path of radius \(r\), then the radius \(r\) is given by (in the usual notation)
The work function of a certain metal is \(3.31 \times 10^{-19}\,J\). Then, the maximum kinetic energy of photoelectrons emitted by incident radiation of wavelength \(5000\,\AA\) is (given \(h = 6.62 \times 10^{-34}\,Js\), \(c = 3 \times 10^8\,m\,s^{-1}\), \(e = 1.6 \times 10^{-19}\,C\))
In the adjacent shown circuit, a voltmeter of internal resistance \(R_v\), when connected across \(B\) and \(C\) reads \(\dfrac{100}{3}\,V\). Neglecting the internal resistance of the battery, the value of \(R_v\) is
Four light sources produce the following four waves: (i) \(y_1 = a\sin(\omega t + \phi_1)\) (ii) \(y_2 = a\sin 2\omega t\) (iii) \(y_3 = a\sin(\omega t + \phi_2)\) (iv) \(y_4 = a\sin(3\omega t + \phi_1)\) Superposition of which two waves give rise to interference?
An infinitely long straight wire has uniform linear charge density of \(\dfrac{1}{3}\,cm^{-1}\). Then, the magnitude of the electric intensity at a point \(18\,cm\) away is (given \(\varepsilon_0 = 8.8 \times 10^{-12}\,C^2N^{-1}m^{-2}\))
Two point charges \(-q\) and \(+q\) are located at points \((0,0,-a)\) and \((0,0,a)\), respectively. The electric potential at a point \((0,0,z)\), where \(z>a\) is
The two lenses of an achromatic doublet should have
Two bar magnets \(A\) and \(B\) are placed one over the other and are allowed to vibrate in a vibration magnetometer. They make \(20\) oscillations per minute when the similar poles of \(A\) and \(B\) are on the same side, while they make \(15\) oscillations per minute when their opposite poles lie on the same side. If \(M_A\) and \(M_B\) are the magnetic moments of \(A\) and \(B\), and \(M_A>M_B\), the ratio \(M_A : M_B\) is
A bar magnet is \(10\,cm\) long and is kept with its north pole pointing north. A neutral point is formed at a distance of \(15\,cm\) from each pole. Given the horizontal component of earth's field is \(0.4\) Gauss, the pole strength of the magnet is
In Young's double slit experiment, the \(10^{th}\) maximum of wavelength \(\lambda_1\) is at a distance \(y_1\) from the central maximum. When the wavelength of the source is changed to \(\lambda_2\), the \(5^{th}\) maximum is at a distance of \(y_2\) from the central maximum. The ratio \(\left(\dfrac{y_1}{y_2}\right)\) is
An ideal gas is subjected to a cyclic process involving four thermodynamic states, among these state \(Q\) and work \(W\) involved in each of these stages are: \(Q_1 = 6000\,J,\; Q_2 = -5500\,J,\; Q_3 = -3000\,J,\; Q_4 = 3500\,J\) \(W_1 = 2500\,J,\; W_2 = -1000\,J,\; W_3 = -1200\,J,\; W_4 = x\,J\) The ratio of the net work done by the gas to the total heat absorbed by the gas is \(n\). The values of \(x\) and \(n\) respectively are
Two cylinders \(A\) and \(B\) fitted with pistons contain equal number of moles of an ideal monatomic gas at \(400K\). The piston of \(A\) is free to move while that of \(B\) is held fixed. Same amount of heat energy is given to the gas in each cylinder. If the rise in temperature of the gas in \(A\) is \(42K\), the rise in temperature of the gas in \(B\) is
Three rods of same dimensions have thermal conductivities \(3K\), \(2K\) and \(K\). They are arranged as shown in the figure. The ends are maintained at \(100^\circ C\), \(50^\circ C\) and \(0^\circ C\). Then, the temperature of the junction in steady state is
Two sources \(A\) and \(B\) are sending notes of frequency \(680\,Hz\). A listener moves from \(A\) and \(B\) with a constant velocity \(u\). If the speed of sound in air is \(340\,m\,s^{-1}\), what must be the value of \(u\) so that he hears \(10\) beats per second?
Two identical piano wires have a fundamental frequency of \(600\) cycles per second when kept under the same tension. What fractional increase in the tension of one wire will lead to the occurrence of \(6\) beats per second when both wires vibrate simultaneously?
In the Young's double slit experiment, the intensities at two points \(P_1\) and \(P_2\) on the screen are respectively \(I_1\) and \(I_2\). If \(P_1\) is located at the centre of a bright fringe and \(P_2\) is located at a distance equal to a quarter of fringe width from \(P_1\), then \(\dfrac{I_1}{I_2}\) is
An ideal gas is subjected to a cyclic process ABCD as depicted in the \(P-V\) diagram given below.
A piece of metal weighs \(45\,g\) in air and \(25\,g\) in a liquid of density \(1.5 \times 10^3\,kg\,m^{-3}\) kept at \(30^\circ C\). When the temperature of the liquid is raised to \(40^\circ C\), the metal piece weighs \(27\,g\) in the density of liquid at \(40^\circ C\) is \(1.25 \times 10^3\,kg\,m^{-3}\). The coefficient of linear expansion of metal is
A clock pendulum made of invar has a period of \(0.5\,s\) at \(20^\circ C\). If the clock is used in a place where temperature averages to \(30^\circ C\), how much time does the clock lose in each oscillation? (For invar, \(\alpha = 9 \times 10^{-7}/^\circ C\), \(g =\) constant)
If the ratio of lengths, radii and Young's modulus of steel and brass wires shown in the figure are \(a\), \(b\) and \(c\) respectively, then the ratio between the increase in lengths of brass and steel wires would be