Recent questions tagged exemplar

An alternating current generator has an internal resistance $R_g$ and an internal reluctance $X_g$.It is used to supply power to a passive loud consisting of a resistance $R_g$ and a reluctance $x_L$ . For maximum power to be delivered from the generator to the load, the value of $X_L$ is equal to

asked Sep 21, 2016 by meena.p

1 answer

If the rms current in a 50 Hz a.c circuit is $5\;A$ , the value of the current $ \large\frac{1}{300}$ seconds after its value becomes zero is

asked Sep 21, 2016 by meena.p

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You are given a $2 \mu F$ parallel plate capacitor .How would you establish an instantaneous displacement current of $1\;MA$ in the space between its plate ?

asked Aug 22, 2016 by meena.p

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What feature of electromagnetic waves led Maxwell to conclude that light itself is electro magnetic wave ?

asked Aug 22, 2016 by meena.p

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The magnetic field of a beam emerging from a filter facing a flood light is given by $B = 12 \times 10^{-8} \sin (1.20 \times 10^7\;z -3.60 \times 10^{15}t)T$ What is the average intensity of the beam ?

asked Aug 22, 2016 by meena.p

1 answer

Electromagnetic wave with wave length $ \lambda$ is used to improve visibillity in runways during fog and most condition

asked Aug 20, 2016 by meena.p

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Electromagnetic wave with wave length $ \lambda$ is used to detect leakage of oil in underground pipe lines

asked Aug 20, 2016 by meena.p

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Electromagnetic wave with wave length $ \lambda$ is used to kill germs in water purifier

asked Aug 20, 2016 by meena.p

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Electromagnetic wave with wave length $ \lambda$ is used in satellite communication . Identify and name the part of electromagnetic spectrum to which these radiation belong

asked Aug 20, 2016 by meena.p

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A variable frequency a.c source is connected to a capacitor .How will the displacement current change with decrease in frequency ?

asked Aug 20, 2016 by meena.p

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The charge on a parallel plate capacitor varies as $q= q_0 \cos 2 \pi \gamma t$ The plates are very large and close together (area aa , separation =d) Neglecting the edge effects, find the displacement current through the capacitor ?

asked Aug 20, 2016 by meena.p

1 answer

Why does microwave over heats up a food item containing water molecules more efficiently ?

asked Aug 20, 2016 by meena.p

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Why is the orientation of the protable radio with respect to broad casting station important ?

asked Aug 20, 2016 by meena.p

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The source of electromagnetic waves can be a charge

asked Aug 20, 2016 by meena.p

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A changed particle oscillates about its means equilibrium position with a frequency of $10^9$ Hz. The electromagnetic wave produced

asked Aug 20, 2016 by meena.p

1 answer

A plane electro magnetic wave propagating along x - direction can have following pair of $\overrightarrow{E}$ and $\overrightarrow{B}$

asked Aug 20, 2016 by meena.p

1 answer

An electro magnetic wave travels in vacuum along z direction $\overrightarrow{E}=(E_1 \hat i +E_2 \hat j) \cos (kz- wt)$ Choose the correct option from the following

asked Aug 19, 2016 by meena.p

1 answer

An EM wave radiation outwards from a dipole antenna with $E_0$ as the amplitude of its electric field vector . The electric field $E_0$ which transports significant energy from the source falls off as

asked Aug 19, 2016 by meena.p

1 answer

If $\overrightarrow{E}$ and $\overrightarrow{B}$ represent electric and magnetic field vectors of the electro magnetic wave is along

asked Aug 19, 2016 by meena.p

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The electric field intensity produced by the radiation coming from $100\;w$ bulls at a $3\;m$ distance is E. The electric field intensity produced by the radiation coming from 50 w bulb at the same distance is :

asked Aug 19, 2016 by meena.p

1 answer

Light with an energy flux of $20w/cm^2$ falls on a non- reflectiy surface has an area of $30\;cm^2$ , the total momentum delivered (for complete absorption ) during 30 minutes is

asked Aug 19, 2016 by meena.p

1 answer

The ratio of contribution made by the electric and magnetic field components to the intensity of an EM wave is

asked Aug 19, 2016 by meena.p

1 answer

A linearly polarized electromagnetic wave given as $E=E_0 \hat i \cos (kz-wt)$ is incident normally on a perfectly reflecting infinite wall at $z=a$ Assuming that the material of the wall is optically inactive , the reflected wave will be given as

asked Aug 19, 2016 by meena.p

1 answer

One requires $11\;ev$ of energy to dissociate a carbon monoxide molecule into carbon and oxygen atoms. The minimum frequency of the appropriate electromagnetic radiation to achieve dissociation lies in

asked Aug 18, 2016 by meena.p

1 answer

Two H atoms in the ground state collide inelastically . The maximum amount by which their combined kinetic energy is reduced is

asked Aug 10, 2016 by meena.p

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What is the minimum energy that must be given to a H- atom in ground state so that it can emit an $H_{\gamma}$ in Balmer series? If the angular momentum of the system is conserved what would be the angular momentum of such $H_{\gamma}$ proton ?

asked Jul 8, 2016 by meena.p

1 answer

When is $H_{\alpha}$ line of the Balmer series in the emission spectrum of hydrogen atom obtained ?

asked Jul 8, 2016 by meena.p

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In which series of hydrogen spectrum , the transition involve the largest changes of energy ?

asked Jul 8, 2016 by meena.p

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When electron falls from a higher energy to a lower energy level , the difference in the energies appear in the form of electromagnetic radiation . Why cannot it be emitted as other form of energy?

asked Jul 8, 2016 by meena.p

1 answer

The mass of a H- atom is less than the sum of the mass of a proton and electron , why is this ?

asked Jul 8, 2016 by meena.p

1 answer

The simple Bohr model is not applicable to $_2He^4$ atom because

asked Jul 8, 2016 by meena.p

1 answer

Let $E_n=\large\frac{-1me^4}{8\in_0^2 n^2h^2}$ be the energy of the nth level of H- atom . If all the H- atoms are in the ground state and radiation of frequency $(E_2-E_1) /h$ falls on it ,

asked Jul 8, 2016 by meena.p

1 answer

The Balmer series for the H- atom can be observed

asked Jul 8, 2016 by meena.p

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The Bohr model for the Spectra of a H-atom

asked Jul 8, 2016 by meena.p

1 answer

Consider aiming a beam of free electron towards free protons. when they scatter , an electron and a proton cannot combine to produce a H-atom .

asked Jul 8, 2016 by meena.p

1 answer

An ionized H- molecules consists of an electron and two protons. The proton are separated by a small distance of the order of any strom .In the ground state ,

asked Jul 7, 2016 by meena.p

1 answer

A set of atoms in an excited state decays

asked Jul 7, 2016 by meena.p

1 answer

Two H atoms in the ground state collide inelastically . The maximum amount by which their combined kinetic energy is reduced is

asked Jul 7, 2016 by meena.p

1 answer

$O_2$ molecules consists of two oxygen atoms. In the molecule , nuclear force between the nuclei of the two atoms

asked Jul 7, 2016 by meena.p

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For the ground state, the electron in th H- atom has an angular momentum = h , according to the simple Bohr model. Angular momentum is a vector and hence there will be infinitely many orbits with the vector pointing in all possible direction . In actuality this is not true.

asked Jul 7, 2016 by meena.p

1 answer

The Simple Bohr model cannot be directly applied to calculate the energy levels of an atom with many electrons . This is because

asked Jul 7, 2016 by meena.p

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The binding energy of a H-atom , considering an electron moving around a fixed nuclei is $B= \large\frac{-me^4}{8n^2\in_0 h^2}$If one decides to work in a frame of reference where the electron is at rest , the proton would be around it. By similar arguments, the binding energy would be , $B=\large\frac{-Me^4}{8n^2\in_0^2h^2}$ This last expression is not correct because ,

asked Jul 6, 2016 by meena.p

1 answer

A neutron beam of energy E scatters from atoms on a surface with a spacing $d= 0.1 nm$ . The first maximum of initially in the reflected beam occurs at $ \theta= 30^{\circ}$ . What is the kinetic energy E of the beam in eV?

asked Jul 4, 2016 by meena.p

1 answer

Two monochromatic beams A and B of equal intensity I , hit a screen . The number of photons hitting the screen by beam A is twice that by beam B. Then What inference can you make about their frequencies ?

asked Jul 4, 2016 by meena.p

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There are two sources of light each emitting with a power of 100 w. one emits X- rays of wave length 1 nm and the other visible light at 500 nm. Find the radio of no of photons of x- rays to the photons of visible light of the given wave length ?

asked Jul 4, 2016 by meena.p

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Do all the electrons that absorb a photon come out as photo electrons ?

asked Jul 4, 2016 by meena.p

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In the explanation of photo electric effect , we assume one photon of frequency $\alpha$ collide with an electron and transfer its energy . This leads to the equation for the maximum energy $E_{max}$ of the emitted electron as $ E_{max}= h \alpha - \phi _0$ where $ \phi _0$ is the work function of the metal. If an electron absorbs 2 photons (each of frequency ) what will be the maximum energy for the emitted electron ?

asked Jul 4, 2016 by meena.p

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A proton and an $\alpha $ particle are accelerated , using the same potential difference . How are the de- Broglie wave length $ \lambda_p$ and $\lambda_{\alpha}$ related to each other ?

asked Jul 4, 2016 by meena.p

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A particle moves in a closed orbit around the orgin . The de- Broglie wave length of the particle varies cyclically between two values $ \lambda_1 , \lambda_2$ with $ \lambda_1 > \lambda_2$ Which of the following statements are true ?

asked Jul 4, 2016 by meena.p

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Photons absorbed in matter are converted to heat , A source emitting n photons/ sec of frequency $\gamma$ is used to convert $1 kg$ of ice at $ 0^{\circ}C$ to water at $ 0^{\circ}C$ . Then , the time taken for the conversion .

asked Jul 4, 2016 by meena.p

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