List of top Physics Questions

A square frame of side 10 cm and a long straight wire carrying current 1 A are in the plane of the paper. Starting from close to the wire, the frame moves towards the right with a constant speed of 10 ms (see figure). The e.m.f induced at the time the left arm of the frame is at x = 10 cm from the wire is :

A thin bar of length $L$ has a mass per unit length $\lambda$, that increases linearly with distance from one end. If its total mass is $M$ and its mass per unit length at the lighter end is $\lambda_{0}$, then the distance of the centre of mass from the lighter end is :

A thin convex lens made from crown glass $\left(\mu=\frac{3}{2}\right)$ has focal length $f$. When it is measured in two different liquids having refractive indices $\frac{4}{3}$ and $\frac{5}{3}$, it has the focal lengths $f_{1}$ and $f_{2}$ respectively. The correct relation between the focal lengths is

A transmitting antenna at the top of a tower has a height $32 \,m$ and the height of the receiving antenna is $50 \,m$. What is the maximum distance between them for satisfactory communication in line of sight (LOS) mode ?

A transverse wave is represented by : $y = \frac{10}{\pi} \sin \left(\frac{2\pi}{T}t-\frac{2\pi}{\lambda}x\right)$ For what value of the wavelength the wave velocity is twice the maximum particle velocity ?

An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level. The open end of the tube is then closed and sealed and the tube is raised vertically up by additional 46 cm What will be length of the air column above mercury in the tube now ? (Atmospheric pressure = $76\, cm$ of Hg)

An ideal monoatomic gas is confined in a cylinder by a spring loaded piston of cros section $8.0 \times 10^{-3} \, m^2$. Initially the gas is at 300K and occupies a volume of $2.4 \times 10^{-3} \, m^3$ and the spring is in its relaxed state as shown in figure. The gas is heated by a small heater until the piston moves out slowly by $0.1\, m$. The force constant of the spring is $8000\, N/m$ and the atmospheric pressure is $1.0 \times 10^5 \, N/m^2$. The cylinder and the piston are thermally insulated. The piston and the spring are massless and there is no friction between the piston and the cylinder. The final temperature of the gas will be : (Neglect the heat loss through the lead wires of the heater. The heat capacity of the heater coil is also negligible)

Assume that an electric field $\vec{E}=30 x^{2} \hat{i}$ exists in space. Then the potential difference $V_{A}-V_{O'}$ where $V_{O}$ is the potential at the origin and $V_{A}$ the potential at $x=2 \,m$ is

Consider a cylinder of mass $M$ resting on a rough horizontal rug that is pulled out from under it with acceleration $'a'$ perpendicular to the axis of cylinder. What is $F_{friction}$ at point $P$ ? It is assumed that the cylinder does not slip.

During the propagation of electromagnetic waves in a medium,

Figure shows a circular area of radius R where a uniform magnetic field $\vec{B}$ is going into the plane of paper and increasing in magnitude at a constant rate. In that case, which of the following graphs, drawn schematically, correctly shows the variation of the induced electric field E(r)?

For sky wave propagation, the radio waves must have a frequency range in between :

Four particles, each of mass M and equidistant from each other, move along a circle of radius R under the action of their mutual gravitational attraction, the speed of each particle is

From a tower of height $H$, a particle is thrown vertically upwards with a speed $u$. The time taken by the particle to hit the ground, is $n$ times that taken by it to reach the highest point of its path. The relation between $H, u$ and $n$ is

In a large building, there are 15 bulbs of 40\, W, 5 bulbs of 100 W, 5 fans of $80\, W$ and 1 heater of $1\, kW$. The voltage of the electric mains is $220 \,V$. The minimum capacity of the main fuse of the building will be :

In materials like aluminium and copper, the correct order of magnitude of various elastic modulii is :

In the circuit shown, current (in A) through the 50 V and 30 V batteries are, respectively :

When a rubber -band is stretched by a distance x, it exerts a restoring force of magnitude $ F = ax + bx^2$, where a and b are constants. The work done in stretching the unstretched rubber-band by $L$ is :

When the rms voltages $V _{ L }, V _{ C }$ and $V _{ R }$ are measured respectively across the inductor $L ,$ the capacitor $C$ and the resistor $R$ in a series LCR circuit connected to an AC source, it is found that the ratio $V _{ L }: V _{ C }: V _{ R }=1: 2: 3$. If the rms voltage of the AC sources is $100 \,V ,$ the $V _{ R }$ is close to:

Three rods of copper , brass and steel are welded together to form a Y-shaped structure .Area of cross -section of each rod is $4cm^2$.End of copper rod is maintained at $100^{\circ}C$ whereas ends of brass and steel are kept at $0^{\circ C}$ Lengths of the copper, brass and steel rods are 46,13 and 12 cm respectively The rods are thermally insulated from surroundings except at ends.Thermal conductivities of copper , brass and steel are 092 , 0.26 and 0.12 in CGS units , respectively .Rate of heat flow throught cooper rod is

On heating water, bubbles being formed at the bottom of the vessel detatch and rise. Take the bubbles to be spheres of radius $R$ and making a circular contact of radius r with the bottom of the vessel. If $r << R$, and the surface tension of water is T, value of r just before bubbles detatch is (density of water is $\rho_{w}$ )

Steel ruptures when a shear of $ 3.5 \times 10^8 \,Nm^{-2}$ is applied. The force needed to punch a $1\, cm$ diameter hole in a steel sheet $0.3\, cm$ thick is nearly :

The angular frequency of the damped oscillator is given by, $\omega = \sqrt{\left(\frac{k}{m} - \frac{r^{2}}{4m^{2}}\right)}$ where $k$ is the spring constant, $m$ is the mass of the oscillator and $r$ is the damping constant. If the ratio $\frac{r^{2}}{mk}$ is $8\%$, the change in time period compared to the undamped oscillator is approximately as follows :

The magnetic properties of a magnet is lost at its

The ratio of $ \frac{C_P}{C_V}$ for a diatomic gas is