List of top Physics Questions

Two cells with the same e.m.f. $E$ and different internal resistances $r_1$ and $r_2$ are connected in series to an external resistance $R$. The value of $R$ so that the potential difference across the first cell be zero is
Which of the following is not due to total internal reflection?
Two radioactive nuclei $P$ and $Q$, in a given sample decay into a stable nucleus $R$. At time $t = 0$, number of $P$ species are $4\, N_0$ and that of $Q$ are $N_0$. Half-life of $P$ (for conversion to $R$) is $1$ minute where as that of $Q$ is $2$ minutes. Initially there are no nuclei of $R$ present in the sample. When number of nuclei of $P$ and $Q$ are equal, the number of nuclei of $R$ present in the sample would be
An ideal gas is compressed isothermally until its pressure is doubled and then allowed to expand adiabatically to regain its original volume ($? = 1.4$ and $2^{-1.4} = 0.38$). The ratio of the final to initial pressure is
The potential energy of a system increases if work is done
A coil has resistance $30$ ohm and inductive reactance $20$ ohm at $50 \,Hz$ frequency. If an ac source, of $200$ volt, $100\, Hz$, is connected across the coil, the current in the coil will be
A current carrying closed loop in the form of a right angle isosceles triangle $ABC$ is placed in a uniform magnetic field acting along $AB$. If the magnetic force on the arm $BC$ is $\vec{F}$, the force on the arm $AC$ is
What fraction of the surface area of earth can be covered to establish communication by one geostationary statellite?
If two bodies stick together after collision and move as a single body, the collision is said to be
Sun is visible a little before the actual sunrise and until a little after the actual sunset. This is due to
If the equivalent capacitance between $P$ and $Q$ of the combination of the capacitors shown in figure below is $ 30\,\mu \,F $ , the capacitor $C$ is
The particle that cannot be accelerated by a cyclotron is
Position-time graph for motion with zero acceleration is
A car moving with a speed of $50 \,km\, h^{-1}$ can be stopped by applying brakes after moving atleast $6 \,m$. If the same car is moving at a speed of $100 \,km\, h^{-1}$ the minimum stopping distance is
The maximum power dissipated in an external resistance R, when connected to a cell of emf E and internal resistance r, will be
A gardener pushes a lawn roller through a distance $ 20\,m $ . If he applies a force of $ 20\,kg\,wt $ in a direction inclined at $ 60^{\circ} $ to the ground, the work done by him is
The current gain of a common base transistor circuit is 0.96. On changing the emitter current by 10.0 mA, the change in the base current will be
Magnetic flux of $10 \mu Wb $ is linked with a coil, when a current of 2 mA flows through it. What is the self inductance of the coil?
Water is used as a coolant in automobile radiators owing to its high
How many $ 1\,\mu F $ capacitors must be connected in parallel to store a charge of $1\, C$ with a potential of $110\, V$ across the capacitors?
A solid sphere rolls down two different inclined planes of same height, but of different inclinations. ln both cases
A circular disc of radius $R$ is removed from a bigger circular disc of radius $2 R$ such that the circumferences of the discs touch. The centre of mass of the new disc is at a distance $\alpha R$ from the centre of the bigger disc. The value of $\alpha$ is
A man stands in a narrow, steep-sided valley. When he shouts he hears two echoes, one after l s and other after 2 s. If the velocity of sound in air is 330 m/s, the width of the valley is
Fusion reaction takes place at high temperature because
An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function $2.75 \,eV$. If the stopping potential of the photoelectron is $10 \,V$ , then the value of $n$ is