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The Bohr model for the spectra of a H-atom: (a) will not apply to hydrogen in the molecular form. (b) will not be applicable as it is for a He-atom. (c) is valid only at room temperature. (d) predicts continuous as well as discrete spectral lines. Choose the correct option:
The displacement-time ($x-t$) graph of a particle performing simple harmonic motion is shown in the figure. The acceleration of the particle at $t = 2$ s is:
Pure $\text{Si}$ at $500\text{ K}$ has an equal number of electron ($n_e$) and hole ($n_h$) concentration of $1.5 \times 10^{16} \text{ m}^{-3}$. Doping by indium increases the hole concentration $n_h$ to $4.5 \times 10^{22} \text{ m}^{-3}$. The doped semiconductor is of:
The moment of inertia of a uniform circular disc of radius $R$ and mass $M$ about an axis touching the disc at its edge and normal to the disc is:
An AC source given by $V = V_m \sin(\omega t)$ is connected to a pure inductor $L$ in a circuit and $I_m$ is the peak value of the AC current. The instantaneous power supplied to the inductor is:
Let En = -(me^4)/(8ε_0^2 n^2 h^2) be the energy of the nth level of H-atom. If all the H-atoms are in the ground state and radiation of frequency (E2 - E1)/h falls on it, then: (a) it will not be absorbed at all. (b) some of the atoms will move to the first excited state. (c) all atoms will be excited to the n=2 state. (d) no atoms will make a transition to the n=3 state. Choose the correct option:
Consider the following Statements A and B and identify the correct answer: Statement A: For a solar-cell, the I-V characteristics lies in the IV quadrant of the given graph. Statement B: In a reverse-biased pn junction diode, the current measured in ($\mu\text{A}$), is due to majority charge carriers.
A block of mass 4 kg is suspended through two light spring balances A and B connected in series. Then A and B will read respectively:
A piece of ice falls from a height $h$ so that it melts completely. Only one-quarter of the heat produced is absorbed by the ice. The value of $h$ is: [Latent heat of ice is $3.4 \times 10^5 \text{ J/kg}$ and $g = 10 \text{ N/kg}$]
A lift of mass $1000 \text{ kg}$ is moving with an acceleration of $1 \text{ m/s}^2$ in the upward direction. Tension developed in the string, which is connected to the lift, is:
The given graph represents the V-I characteristic for a semiconductor device. Which of the following statements is correct?
A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6A, the voltage across the secondary coil and the current in the primary coil respectively are:
A solid cylinder of mass $2 \text{ kg}$ and radius $4 \text{ cm}$ is rotating about its axis at the rate of $3 \text{ rpm}$. The torque required to stop after $2\pi$ revolutions is:
Three identical spherical shells, each of mass $m$ and radius $r$ are placed as shown in the figure. Consider an axis $XX'$, which is touching two shells and passing through the diameter of the third shell. The moment of inertia of the system consisting of these three spherical shells about the $XX'$ axis is:
In the following circuit, the output Y for all possible inputs A and B is expressed by the truth table:
A solid cylinder of mass $3 \text{ kg}$ is rolling on a horizontal surface with a velocity of $4 \text{ ms}^{-1}$. It collides with a horizontal spring of force constant $200 \text{ Nm}^{-1}$. The maximum compression produced in the spring will be:
The moment of inertia of a thin rod about an axis passing through its mid-point and perpendicular to the rod is $2400\text{ g cm}^2$. The length of the $400\text{ g}$ rod is nearly:
A solid sphere is in rolling motion. In rolling motion, a body possesses translational kinetic energy ($K_t$) as well as rotational kinetic energy ($K_r$) simultaneously. The ratio $K_t : (K_t + K_r)$ for the sphere will be:
A standard filament lamp consumes 100 W when connected to a 200 V AC mains supply. The peak current through the bulb will be:
A black body at $227^\circ\text{C}$ radiates heat at the rate of $7 \text{ cal cm}^{-2}\text{s}^{-1}$. At a temperature of $727^\circ\text{C}$, the rate of heat radiated in the same units will be: