List of top Physics Questions

The colour of the green flower seen through red glass appears to be dark. Red glass transmits only red light.
: The alternating current lags behind the e.m.f. by a phase angle of $\pi / 2$, when AC flows through an inductor. : The inductive reactance increases as the frequency of $A C$ source decreases.
An electric motor will have maximum efficiency when back emf becomes equal to half of applied emf. Efficiency of electric motor depends only on magnitude of back emf.
An object $5\, cm$ tall is placed $1\, m$ from a concave spherical mirror which has a radius of curvature of $20 \,cm$. The size of the image is
Alternating current cannot be measured by $D.C.$ ammeter because
Activity of a radioactive sample decreases to $ (1/3)^{rd} $ of its original value in 3 days. Then, 1 in 9 days its activity will become
A transverse wave propagating along x-axis is represented by $ y(x,t)=8.0\sin \left( 05\pi x-4\pi t-\frac{\pi }{4} \right) $ where $x$ is in metre and $t$ is in second. The speed of the wave is
A car of mass m moves in a horizontal circular path of radius $r\,m$. At an instant its speed is v $ ms^{ - 1 } $ and is increasing at a rate of a $ ms^{ - 2}$ . Then the acceleration of the car is
An $\alpha -$ particle of energy 5 MeV is scattered through $180 ^\circ $ by a fixed uranium nucleus. The distance of the closest approach is of the order of
A spring of spring constant $5 \times 10^3 Nm^{-1}$ is stretched initially by 5 cm from the unstretched position. Then the work required to stretch it further by another 5 cm is
Two stretched strings have lengths $l$ and $2l$ while tension are $T$ and $4T$ respectively. If they are made of same material the ratio of their frequency is
Which one of the following statements is true?
What causes chromatic aberration?
A particle of mass $m$ moves with constant speed along a circular path of radius $r$ under the action of force $F .$ Its speed is
A motor is used to deliver water at a certain rate through a given horizontal pipe. To deliver $n$-times the water through the same pipe in the same time the power of the motor must be increased as follows
A microscope is focused on a mark on a piece of paper and then a slab of glass of thickness $3 \,cm$ and refractive index $1.5$ is placed over the mark. How should the microscope be moved to get the mark in focus again?
A metal wire of linear mass density of 9.8 g/m is stretched with a tension of 10 kg-wt between two rigid supports 1 m apart. The wire passes at its middle point between the poles of a permanent magnet and it vibrates in resonance when carrying an alternating current of frequency n. The frequency n of the alternating source is
A material B? has twice the specific resistance of ?A?. A circular wire made of B? has twice the diameter of a wire made of ?A?. Then for the two wires to have the same resistance, the ratio $l_{B} / l_{A} $ of their respective lengths must be :
A machine is delivering constant power to drive a body along a straight line. What is the relation between the distance travelled by the body against time
A long solenoid has 200 turns per cm and carries a current i. The magnetic field at its centre is 6.28 x$10^{-2}$ weber/$m^{2}$. Another long solenoid has 100 turns per cm and it carries a current i/3. The value of the magnetic field at its centre is:
A liquid drop of radius $ R $ breaks into $64$ tiny drops each of radius $ r $ . If the surface tension of the liquid is $ T $ , then the gain in energy is
A liquid does not wet the solid surface if the angle of contact is
A light spring balance hangs from the hook of the other light spring balance and a block of mass M kg hangs from the former one. Then the true statement about the scale reading is
The physical quantity having the dimensions $\left[ M ^{-1} L ^{-3} T ^{3} A ^{2}\right]$ is
A battery of emf $10\, V$ and internal resistance $3\, \Omega$ is connected to a resistor. The current in the circuit is $0.5\, A$. The terminal voltage of the battery when the circuit is closed is