Recent questions and answers in Physics

The moment of inertia of a thin circular disc about an axis passing through its centre and perpendicular to its diameter and touching the edge of the rim is

answered Dec 3, 2021 by n.abhiram2005

2 answers

Two bodies $A$ and $B$ of equal surface area have thermal emissivities of $0.01$ and $0.81$ respectively. The two bodies are radiating energy at the same rate. Maximum energy is radiated from the two bodies A and B at wavelengths $\lambda _A$ and $\lambda_B$ respectively. Difference in these two wavelength is $1 \; \mu m $. If the temperature of the body A is $5802\;K,$ then value of $\lambda _B$ is

answered Sep 16, 2020 by sivasaijoshi

1 answer

At a given instant of time the position vector of a particle moving in a circle with a velocity $3 \hat i- 4 \hat j + 5 \hat k$ is $\hat i+9 \hat j -3 \hat k$. Its angular velocity at that time is :

answered May 29, 2020 by singi.nagireddy

1 answer

From Bohr's theory when electrons jump from higher energy orbits to second orbit spectral lines that occur belongs to ................ series.

answered Apr 26, 2020 by abhiranpabolu

1 answer

A radioactive source has a half- life of 3 hours. A freshly prepared sample of the same exhibits radioactivity 16 times the permissible safe value. The minimum time after which it would be possible to work safely with the source is ............ hours.

answered Apr 16, 2020 by sreekarreddy369

1 answer

A ball of 1 g released down an inclined plane describes a circle of radius 10 cm in the vertical plane on reaching the bottom. The minimum height of the inclined plane is ................ cm.

answered Sep 11, 2019 by meena.clay6

1 answer

In Young's double slit experiment, the 10th maximum. When the wavelength $\lambda _1$ is at a distance of $y_1$ from the central maximum. When the wavelength of the source is changed to $\lambda_2,5$ th maximum is at a distance of $y_2$ from its central maximum. The ratio $\bigg(\large\frac{y_1}{y_2}\bigg)$is :

answered Aug 29, 2019 by shaikabdulsattar69

3 answers

Magnetic field induction at the center of a circular coil of radius 5 cm and carrying a current 0.9 A is (in SI units) ($\in _0$= absolute permittivity of air in SI units, velocity of light $= 3 \times 10^8 ms^{-1})$

answered Jul 3, 2019 by rohithareddy.bhimavarapu2003

1 answer

The ratio of magnetic moments of two short magnets which give deflection in $\tan B$ position when placed at $12\;cm$ and $18\;cm$ from center of a deflection magnetometer is ................... .

answered May 3, 2019 by suhaibbawani9

1 answer

In photoelectric effect the slope of straight line graph between stopping potential and frequency of incident radiation gives the ratio of Planck constant to ................ .

answered Mar 10, 2019 by jatt61619

2 answers

The liquid does not wet the solid surface if the angle of contact is

answered Jan 29, 2019 by mdhussainbit

1 answer

Twelve cells, each having emf E volts are connected in series and are kept in a closed box. Some of these cells are wrongly connected with positive and negative terminals reversed. This 12 cell battery is connected in series with an ammeter , an external resistance R ohms and a two- cell battery (two cells of the same type used earlier , connected perfectly in series). The current in the circuit when the 12 - cell battery and 2-cell battery aid each other is 3A and is 2A when they oppose each other . Then, the number of cells in 12 -cell battery that are connected wrongly is :

answered Jan 24, 2019 by skbhatta1957

2 answers

The threshold frequency of the metal of the cathode in a photoelectric cell is $ 1 \times 10^{15}\: Hz$ . When a certain beam of light is incident on the cathode, it is found that a stopping potential '4.144 V' is required to reduce the current to zero. The frequency of the incident radiation is : $ ( h = 6.63 \times 10^{-34} J-s)$

answered Dec 29, 2018 by aaaunnipapu

3 answers

Two solid spheres (A and B) are made of metals of different densities $p_A$ and $p_B$ respectively. If their masses are equal, the ratio of their moments of inertia $(I_B / I_A)$ about their respective diameter is

answered Dec 26, 2018 by innovate612

1 answer

The focal length of an equi-convex lens is greater than the radius of curvature of any of the surfaces. Then the refractive index of the material of the lens is :

answered Nov 24, 2018 by tejaswanidevdhari2839

1 answer

An ideal gas is initially at temperature T and volume V. Its volume is increased by $ \Delta V$ due to an increase in temperature $ \Delta T$ , pressure remaining constant. The physical quantity $ \delta = \large\frac{\Delta V}{V \Delta T}$ varies with temperature as :

answered Nov 10, 2018 by thagee.vedartham

1 answer

A wheel of radius 0.4 m can rotate freely about its axis as shown in the figure. A string is wrapped over its rim and a mass of 4 kg is hung. An angular acceleration of $8\;rad-s^{-2}$ is produced in it due to the torque. Then moment of inertia of the wheel is :

answered Oct 31, 2018 by apurvtarkas22

1 answer

When boron is added as impurity to silicon, the resulting material is ................. semiconductor.

answered Oct 24, 2018 by sadafkhansalvia786

1 answer

A ray of light refracts from medium 1 into a thin layer of medium 2, crosses the layer and is incident at the critical angle on the interface between the medium 2 and 3 as shown in figure. If the angle of incidence of ray is $\theta$, the value of $\theta$ is :

answered Jul 27, 2018 by hariprasadr77

3 answers

Consider a parallel plate capacitor of capacity 10 $ \mu\: F$ filled with air. When the gap between the plates is filled partly with a dielectric constant 4, as shown in figure.The new capacity of the capacitor is ( A is the area of plates ) :

answered Jun 3, 2018 by libradeep026

2 answers

A photon of energy 'E' ejects a photo electron from a metal surface whose work function is $W_0$. If this electron enters into a uniform magnetic field of induction 'B' in a direction perpendicular to the field and describes a circular path of radius 'R' , then the radius 'r' is given by , (in the usual notation):

answered Apr 28, 2018 by vijay0123.vs

2 answers

A magnet of length 10 cm and magnetic moment $1 Am^2$ is placed along the side AB of an equilateral triangle ABC. If the length of sides AB is 10 cm, the magnetic induction at point C is :

answered Apr 9, 2018 by sahilumraosahilumrao2001

2 answers

A sonometer wire has a length of $114$ cm, between two fixed ends. Where should two bridges be placed so as to divide the wire into three segments (in cm) whose fundamental frequencies are in the ratio 1 : 3 : 4 ?

answered Jan 31, 2018 by rahulpanghal1450

2 answers

Two blocks of masses $1\;kg$ and $2\;kg$ are connected by are connected by a metal wire going over a smooth pulley. The breaking stress of metal is $\large\frac{40}{3 \pi}$$\times 10^6\;Nm^{-2}$.What should be the minimum radius of wire used if it should not break? $(g=10\;m/s^{-2})$

answered Jan 20, 2018 by harshalg8454

2 answers

If the escape velocity on earth is 11.2 km/sec, its value for a planet having double the radius and 8 times the mass of earth is .............. m/s.

answered Oct 26, 2017 by gsrkomali

1 answer

A uniform chain of length $L$ is lying on the horizontal table . If the coefficient of friction between the chain and the table top is $\mu'$ , what is the maximum length of the chain that can hang over the edge of the table without disturbing the rest of the chain on the table?

answered Oct 9, 2017 by ramendrarajput5

2 answers

A ball is dropped into a well. The water level in the well is at a depth 'h' below the top. If the speed of sound is V, then after what time the splash of sound is heard?

answered Oct 7, 2017 by aryanchhetri123

2 answers

A piece of metal weights 45 gms in air and 25 gms in a liquid of density $1.5 \times 10^3kg-m^{-3}$ kept at $30^{\circ}C. $ When the temperature of the liquid of density $1.5 \times 10^3\;kg-m^{-3}$ kept at $30^{\circ}C$. When the temperature of the liquid is raised to $40^{\circ}$, the metal piece weight 27 gms. The density of liquid at $40^{\circ}C$ is $1.25 \times 10^3\;kg-m^{-3}.$ The coefficient of linear expansion of metal is :

answered Jul 14, 2017 by kondaveetiprabhakar

1 answer

The focal length of a lens of dispersive power $0.45$ which should be placed in contact with a convex lens of focal length $84\;cm$ and dispersive power $0.21$ to make the achromatic combination from the two lenses, in cm is :

answered May 23, 2017 by harshitsri1090

2 answers

The refracting angle of a prism is A and the refractive index of the material of the prism is $\cot (A/2)$. The angle of minimum deviation of the prism is :

answered Apr 27, 2017 by khushboo.rani5419

1 answer

Two capillary tubes A and B are arranged in parallel. A liquid flows through these capillary tubes under the same pressure head. Both the tubes have a same length. The radii of A and B are r and $\large\frac{r}{2}$ respectively. If the rate of flow of liquid through A is $8\: cm^3/s$ , then the rate of flow through the combination of A and B is

answered Feb 25, 2017 by adityasher2000

2 answers

The center of mass of three particles of masses 1 kg,2 kg and 3 kg is at (2,2,2). The position of the fourth mass of 4 kg to be placed in the system as that the new center of mass is at (0,0,0) is :

answered Sep 13, 2016 by ruttulahimana37

2 answers

The heat evolved for the rise of water when one end of the capillary tube of radius r is immersed vertically into water is : (Assume surface tension=T and density of water to be p)

answered Apr 24, 2016 by vermasrijan

1 answer

A ray of light passes through an equilateral prism such that the angle of incidence is equal to the angle of emergence and each one is equal to $\large\frac{3}{4}$ th the angle of prism. Then angle of deviation is :

answered Feb 3, 2016 by yuks.psbbm

2 answers