List of top Physics Questions

Two coils have mutual inductance \(0.5\,\text{H}\). If the current in the primary coil changes at the rate of \(4\,\text{A s}^{-1}\), the induced emf in the secondary coil is

A galvanometer of resistance \(50\,\Omega\) gives full-scale deflection when a current of \(2\,\text{mA}\) passes through it. The value of shunt resistance required to convert it into an ammeter of range \(2\,\text{A}\) is

The electric field strength at a point in an electric field is $30\,N/C$. Find the force experienced by a charge of $20\,C$ at that point.

$100\,\text{g}$ of water at $60^\circ C$ is added to $180\,\text{g}$ of water at $95^\circ C$. The resultant temperature of mixture is

Sodium and Copper have work functions 2.3 eV and 4.5 eV respectively. Then the ratio of their threshold wavelengths is nearly:

Energy released in the fission of a single \( {}_{92}\text{U}^{235} \) nucleus is 200 MeV. The fission rate of a \( {}_{92}\text{U}^{235} \) fueled reactor operating at a power level of 5W is:

An electron is moving in an orbit of hydrogen atom in which there can be a maximum of six transitions. Another electron is moving in another orbit of hydrogen atom in which there can be a maximum of three transitions. The ratio of the velocity of electrons in these two orbits is:

A TV transmitting antenna is 81 m tall. Service area covered, if the receiving antenna is at the ground level, will be about:

In the logic circuit, if A=1 and B=1, the outputs \( \text{Y}_{3} \) and Y are respectively:

A solar cell has a light gathering area of \( 10\,\text{cm}^{2} \) and produces 0.2 A at 0.8 V (D.C.) when illuminated with sunlight of intensity \( 1000\,\text{Wm}^{-2} \). The efficiency of the solar cell is:

A circular coil of radius 8 cm, 400 turns and resistance \( 2\,\Omega \) is placed with its plane perpendicular to the horizontal component of the earth's magnetic field. It is rotated about its vertical diameter through \( 180^{\circ} \) in 0.30 sec. Horizontal component of the earth's magnetic field at the place is \( 3\times10^{-5} \) T. The magnitude of current induced in the coil is approximately:

A particle of charge 'q' and mass 'm' starts moving from the origin under the action of electric field, \( \vec{E}=E_{0}\hat{i} \) with a velocity \( v=v_{0}\hat{j} \). The time taken to increase its velocity to \( \frac{\sqrt{5}}{2} v_0 \) is:

An ac source has a peak voltage \( \frac{200}{\sqrt{2}} \) V and frequency 50 Hz. The value of voltage after \( \frac{1}{600} \) s from the start is:

Two identical short bar magnets, each having a magnetic moment of 10 \( \text{Am}^{2} \) are arranged such that their axial lines are perpendicular to each other and their centres be along the same straight line in a horizontal plane. If the distance between their centres is 0.2 m, the resultant magnetic induction at a point midway between them is: (\( \mu_{\circ}=4\pi\times10^{-7}~\text{Hm}^{-1} \))

A circular coil connected to a battery of emf E produced a magnetic field at its centre. The coil is unwound, stretched to double its length and rewound into a coil of \( \left(\frac{1}{3}\right)^{\text{rd}} \) of its initial radius. If this coil is connected to a battery of emf E' to produce same magnetic field at its centre, then E' is:

\( 1\,\mu\text{C} \), \( -1\,\mu\text{C} \) charges are placed at a distance of 5 cm in forming a dipole. The amount of torque required to place this dipole perpendicular to an electric field of \( 3\times10^{5}~\text{NC}^{-1} \) is given by:

In the circuit shown in the figure, the current (I) is 6 A when \( R_{3} \) is infinite and current (I) is 9 A when \( R_{3} \) is short circuited. Then the values of \( R_{1} \) and \( R_{2} \) are respectively:

As shown in the figure two capacitors \( C_{1} \) \& \( C_{2} \) each having same gap between the plates x filled with different media of dielectric constants 3K and 6K respectively. If these two capacitors are connected to a battery, the ratio of potential differences across dielectric layers of \( C_{1} \) and \( C_{2} \) is:

The net outward flux through surface of a box is \( 8.0\times10^{3}~\text{Nm}^{2}\text{C}^{-1} \). The net charge inside the box is (approximately):

The current \( I_{3} \) in the given circuit is:

A compound microscope consists of an objective lens of focal length \( f_{o}=1~\text{cm} \) and an eyepiece of focal length \( f_{e}=5~\text{cm} \). An object is placed 1.2 cm in front of the objective. The final image is formed at the least distance of distinct vision. The nature of the intermediate image and the total magnification of the microscope are:

How fast a person should drive his car so that the red signal of light appears green? (wavelengths of red and green colours are 6200 and 5400 respectively)

A sound source of 1000 Hz frequency approaches the observer with speed \( 20~\text{ms}^{-1} \). The observed frequency of sound is nearly: (speed of sound in air \( = 340~\text{ms}^{-1} \))

If a person cannot see objects closer than 100 cm, the power of lens required to read at 25 cm is:

An ideal gas is taken through the cycle \( A\rightarrow B\rightarrow C\rightarrow A \) as shown in figure. If the net heat supplied to the gas in the cycle is 10 J, the work done in the process \( C\rightarrow A \) is: