List of top Physics Questions

A long string with a charge of a per unit length passes through an imaginary cube of edge L.
The maximum possible flux of electric field through the cube will be

Three sound waves of equal amplitudes have frequencies $(n - 1), n, (n + 1)$. They superimpose to give beats. The number of beats produced per second will be

The second overtone of an open organ pipe has the same frequency as the first overtone of a closed pipe $L$ metre long. The length of the open pipe will be

Two cars $P$ and $Q$ start from a point at the same time in a straight line and their positions are represented by $x _{ P }( t )= at + bt ^{2}$ and $x _{ Q }( t )=f t - t ^{2}$. At what time do the cars have the same velocity ?

Three liquids of densities having the same value of surface tension $T$, rise to the same height in three identical capillaries. The angles of contact $\theta_{1}, \theta_{2}$ and $\theta_{3}$ obey-

The half-life of a radioactive substance is $30$ minutes. The time (in minutes) taken between $40\%$ decay and $85\%$ decay of the same radioactive substance is

The given circuit has two ideal diodes connected as shown in the figure below. The current flowing through the resistance \(R_1\) will be

When a metallic surface is illuminated with radiation of wavelength $\lambda$ , the stopping potential is V. If the same surface is illuminated with radiation of wavelength $2 \lambda$, the stopping potential is $\frac{V}{4}$ . The threshold wavelength for the metallic surface is :

For $CE$ transistor amplifier, the audio signal voltage across the collector resistance of $2 k \Omega$ is $4\, V$. If the current amplification factor of the transistor is $100$ and the base resistance is $1 \, k\Omega$, then the input signal voltage is

Electrons of mass $m$ with de-Broglie wavelength $\lambda$ fall on the target in an X-ray tube. The cutoff wavelength $(\lambda_0)$ of the emitted X-ray is

Consider the junction diode as ideal. The value of current flowing through \(AB\) is :

An electron of mass m and a photon have same energy E. The ratio of de-Broglie wavelengths associated with them is :

An electric dipole is placed at an angle of $30^{\circ}$ with an electric field intensity $2 \times 10^{5} N / C .$ It experiences a torque equal to $4\, Nm$. The charge on the dipole, if the dipole length is $2\, cm$, is

A rectangular film of liquid is extended from $(4 \, cm \times 2\, cm)$ to $ (5 \, cm \times 4 \, cm)$. If the work done is $3 \times 10^{-4} \, J$, the value of the surface tension of the liquid is -

A $n-p-n$ transistor is connected to common emitter configuration in a given amplifier. A load resistance of $800$ is connected in the collector circuit and the voltage drop across it is $0.8\, V$. If the current amplification factor is $0.96$ and the input resistance of the circuit is $192\,\Omega$, the voltage gain and the power gain of the amplifier will respectively be

A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by $60^{\circ}$ is $W$. Now the torque required to keep the magnet in this new position is

Plancks constant $(h)$, speed of light in vacuum $(c)$ and Newton?s gravitational constant $(G)$ are three fundamental constants. Which of the following combinations of these has the dimension of length?

Which of the following combinations should be selected for better tuning of an $L-C-R$ circuit used for communication ?

When an $\alpha$-particle of mass 'm' moving with velocity 'v' bombards on a heavy nucleus of charge 'Ze', its distance of closest approach from the nucleus depends on m as :

Two non-mixing liquids of densities $\rho$ and $ n\rho (n > 1)$ are put in a container. The height of each liquid is h. A solid cylinder of length L and density d is put in this container. The cylinder floats with its axis vertical and length $ pL (p < 1)$ in the denser liquid. The density d is equal to :

Two identical glass $(\mu_g = 3/2)$ equiconvex lenses of focal length $f$ each are kept in contact. The space between the two lenses is filled with water $(\mu_w = 4/3)$. The focal length of the combination is

Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at $100^{\circ} C$ , while the other one is at $0^{\circ} C$. If the two bodies are brought into contact, then, assuming no heat loss, the final common temperature is -

The ratio of escape velocity at earth $v_e$ to the escape velocity at a planet $v_p$ whose radius and mean density are twice as that of earth is :

The potential differences across the resistance, capacitance and inductance are $80\, V$, $40\, V$ and $100\, V$ respectively in an $L-C-R$ circuit . The power factor of this circuit is

The potential difference \((V_A - V_B)\) between the points \(A\) and \(B\) in the given figure is