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Physics Questions and Answers October 09, 2022

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Imagine that a reactor converts all given mass into energy and that it operates at a power level of 10 9 watt. The mass of the fuel consumed per hour in the reactor will be (velocity of light, c = 3 x 10 8 m/s). (a) 0.96 gm (b) 0.8 gm (c) 4 x 10 -2 gm (d) 6.6 x 10 -5 gm

Que Them energy levels for a particle of mass m in the potential V(x) xx1, determined in the WKB approximation Jam EV(x) dx (n1) kx a where a 4 b are turning points n 0,1,2,) are a) En tad n) 3 by En tax (nd)73 c 23 En (m) tax d Fn ters (1) En Jam 3
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Calculate the energy of nth state for a particle of mass m moving in potential V(x) infinity x 0 By using wkB approximation method

when laser light of wavelength Iemdba falls on a metal scale with 1mm engravings at a grazing angle of incidences, it is diffracted to form a vertical chain of diffracted spots on a screen kept lar to the scale. If the wavelength of the laser is increased by 200nm, the angle of the firstorder diffraction spot changes from 5 to.

XRay of wavelength lembdaa is reflected from the (111) plane of Simple cubic lathice. If the latrice constant is a the corresponding Bragg angle is

The potential of a molecule as a function of the distance between the atoms is given by v(r) ar6 br12,The value of the potential at equilibrium seperation between the atoms is

The dispersion relation of photons in a solid isw2(k) w23cosKxaCosKya cosKza The velocity of Photons at larger wavelength is

The Phonon dispersion for the following 1Dim. diatomic lattice with masses M1 M2 is given by w2(q)k(1m11m2) where a is the lattice parameter and K is the spring constant. The velocity of sound is

If the number density of a free e gas in 3D is increased 8 times, its fermi temp. will be

Using the frequency dependent drude formula what is the effective kinetic inductance of metallic wire that is to be used as a bansmission line

In a Band structure calculation, the dispersion relation for es is found to be epsilon(k) (coskxa coskya coskza) The effective mass at the boundary of the first Bz is

The dispersion relation for elections in an FCC Crystal is given in tight binding approx.) by E(k)4 t cos Kxa2 cos Kya2 cos Kya2 cos K2a2 cos K2a2 cos Kxa2 The xcomponent of velocity of the elections at (piea,0,0) is,a 260 b) 2000 ds

The band energy of an election in a crystal for a particular Kdirection has the form E(k) AB cos2ka where AB are the positive constants and 0

A sample of si has election and Role mobility of 0.13 0.05 m2vs respectively at 300k. It is doped with P and Al with doping densities of 1.5x1021 m3 and 2.5 X 1021m3 serpectively. The conductivity of the doped si sample at 300k.

From a surface, light of wavelength 3125A and 3650A causes emission of electrons whose maximum kinetic energy is 2.128ev

The concentration of elections n and holes p for an intrinsic semiconductor at temperature T can be explained as npAT32 expEg2KBT) where Eg is the band gap and A is a constant.,If the mobility of both types of carriers is proportional to T32, then the log of the conductivity is a linear function of T1 with slope

A magnetic field sensor based on the hall effect is to be fabricated by implanting as into si film of thickness 1 muonm. The specifications, require a magnetic field sensitivity of 500 mv T at an excitation current of 1 MA. The implantation does to be adjusted such that the average cassier density, after activation is

Light of wavelength 600 nm and power of 1 mw is incident on a semiconductor photodiode with an absorbing layer of thickness of (ln 4 muonm) I) If the absorption coefficent at this wavelength is 104 cm1 and if 1 power is lost on reflection at the surface, the power absorbed will be

Monochromatic light of wavelength 660nm and intensity 100 mwcm2 falls on a solar cell of area 30 cm2. The conversion efficiency. of the solar cell is 10. If each converted photon results in IEHP, what is the maximum circuit cument supplied by the solar cell

The power density of sunlight incident on a solar cell is 100 mwcm2. Its short circuit curent density is 30 mAcm2 of open circuit voltage is 0.1V. If the fill factor of the solar cell decreases from 0.8 to 0.5 then the efficency will decreases from

An LED operates at 1.5V and 5mA in Forward bias. Assuming an 80 external efficency of the LED, how many photons are emitted per second

If the static dielectric constant of Nacl crystal is 5.6 and its optical refractive index is 1.5, the ratio of its electric polarizability to its total Polarizability is

Calculate the de Broglie wavelength of an election having a kinetic energy of 1000 ev. Compare the result with the wavelength of Xrays having the same energy

The magnetisation M of a Ferromagnet, as a function of the temperature T and the magnetic field is described by the equation M tanh (TcT M HT) In these units, the zero field magnetic susceptibility in terms of M (0) M (H0) is

The critical magnetic fields of a superconductor at temperatures 4K and 8k are 11mAm and 5.5 mAm respectively. Then transition temp. is

Electron scattering experiment gives a value for the radius. 2x10m a a sucleus. Estimate the order of energies of of electrons used for the experiment. Use relativistic ompressions. For scattering experimpert 11

In the network of Figure 2.59, R, 102 and R, 20 02. Compute the current i supplied by the 15 V source. 15 V R R R R R R R R R R R R Figure 2.59. Circuit for Problem 6 Hint Start at the right end and by series and parallel combinations of the resistors, reduce the cir cuit to a simple series circuit. This method is known as analysis by network

In the circuit of Figure 2.60, use the voltage division expression to compute vy and vy 592 16 V 2002 1002 24 V 40 2 Figure 2.60. Circuit for Problem 7

In the circuit of Figure 2.61, use the current division expression to compute ix and iy. 16 A 1x 350 2002 (1) 24 A Figure 2.61. Circuit for Problem 8 1092 40 52

A transformer consists of two separate coils (inductors) wound around an iron core as shown in Figure 2.62. There are many turns in both the primary and secondary coils but, for simplicity, only few are shown. It is known that the primary coil has a resistance of 5.48 2 at 20 degrees Celsius. After two hours of operation, it is found that the

A new facility is to be constructed at a site which is 1.5 miles away from the nearest electric utility company substation. The electrical contractor and the utility company have made load calcula tions, and decided that the main lines from the substation to the facility will require several cop per conductors in parallel. Each of these conductors

The transition temperature of a BCS superconductor with an average atomic mass of 199.5 is 4.185k. what is the transition temperature for an average atomic mass of 203.4

The equivalent resistance of a voltmeter is 140,000 2. The voltmeter uses a galvanometer that has a full scale deflection of 180 A. What is the maximum voltage that can be measured by the voltmeter

Three identical single phase transformers each of rating 5 kVA, 200V100V, 50Hz are connected in deltadelta. Calculate what line to line voltage to be applied to the HV side Also find out corresponding LV side line to line voltage. Find out the kVA rating of the bank such that none of the transformers get over loaded.

In the circuit of Figure 2.54, the voltage source and both resistors are variable. Power Supply (Voltage Source) Vs Figure 2.54. Circuit for Problem 1 a. With vs 120 V, R, 70 52, and R 50 52, compute the power absorbed by R.. Answer 50 w b. With vs 120 V and R, 02, to what value should R be adjusted so that the power absorbed by it will be 200

A box, seperated by a movable ball, has two Compartments are equal, but the pressure are 3P Po, respectively, when the walls is allowed. to move, the final Pressure in the two compart ments becomes equal. The final pressure is

In the circuit of Figure 2.55, RLOAD represents the load of that circuit. 3 A wwww. 592 SA 75 V Compute a. ILOAD Answer 8 A b. VLOAD Answer 20 V c. PLOAD Answer 160 w 1 10 (2 24 V wwww 202 LOAD VLOAD PLOAD RLOAD Figure 2.55. Circuit for Problem 2

For the circuit of Figure 2.56, compute the power supplied or absorbed by each device. 24 A 6 A B A 12 V C 60 V 36 V Figure 2.56. Circuit for Problem 3

In the circuit of Figure 2.57, compute the power delivered or absorbed by the dependent voltage source. 50 V R 2Q R 3100 W 10 A R 6 Sing Figure 2.57. Circuit for Problem 4 R 102

In the network of Figure 2.58, each resistor is 10 52. Compute the equivalent resistance Req Reg Zum I Figure 2.58. Circuit for Problem 5

A 400V, 3phase star connected alternator supplies a deltaconnected load, each phase of which has a resistance of 30 and inductive reactance 40. Calculate (a) the current supplied by the alternator and (b) the output power and the kVA of the alternator, neglecting losses in the line between the alternator and load.

Three loads, each of resistance 30, are connected in star to a 415 V, 3phase supply. Determine (a) the system phase voltage, (b) the phase current and (c) the line current. (MAY09)

Two different thermodynamic systems are b described by the following eqn of state 1T13RN12U1 1T25RN22U2 where T(1,2) , N (1,R) U(1,2) are respectively, the temperatures, the mole numbers the internal energy of the two systems, and Ris the gas constant. Let Utot denote the total energy when these two systems are but in contact and attain thermal

An autotransformer has a coil with total number of turns NCD 200 between terminals C and D. It has got one tapping at A such that NAC 100 and another tapping at B such that NBA 50. Calculate currents in various parts of the circuit and show their directions when 400 V supply is connected across AC and two resistive loads of 600 400 are

A 5kVA, 200 V 100 V, 50 Hz, single phase ideal two winding transformer is to used to step up a voltage of 200 V to 300 V by connecting it like an auto transformer. Show the connection diagram to achieve this. Calculate the maximum kVA that can be handled by the autotransformer (without over loading any of the HV and LV coil). How much of this kVA

calculate the work done by the gas if temperature of 2 moles of an ideal gas is increased from To to 2To through the process PT2Constant.

A series LRC circuit has a sinusoidal input voltage of maximum value 12 V. If inductance, L 20 mH, resistance, R80 Q2, and capacitance, C 400 nF, determine (a) the resonant frequency, (b) the value of the p.d. across the capacitor at the resonant frequency, (c) the frequency at which the p.d. across the capacitor is a maximum, and (d) the value of

A pure inductance of 1.273 mH is connected in series with a pure resistance of 30 2. If the frequency of the sinusoidal supply is 5 kHz and the p.d. across the 300 resistor is 6 V, determine the value of the supply voltage and the voltage across the 1.273 mH inductance. Draw the phasor diagram. (MAY07)

An alternating current i 414 Sin (2 x 50 x t) A is passed through a series circuit of a resistance of 1002 and an inductance of 0.31831 H. find the expression for the instantaneous values of voltage across, (MAY08) a. The resistance, b. Inductance c. Capacitance

The wave form of the voltage and current of a circuit are given by e 120 Sin (314 t) i 10 Sin (314 tm6) Calculate the value of resistance, capacitance which is connected in series to form the circuit. Also, Draw wave forms for current, voltage and phasor diagram. Calculate power consumed by the circuit.

A resistance of 12092 and a capacitive reactance of 25052 are connected in series across a AC voltage source. If a current 0.9 A is flowing in the circuit find out, (i). Power factor (ii). Supply voltage (iii). Voltage across resistance and capacitance (iv). Active power and reactive power (JUN09)

A series circuit consisting of 252 resistor, 64mH inductor and 80uF capacitor to a 110V, 50Hz, Single phase supply as shown in fig. Calculate the current, Voltage across individual element and overall p.f of the circuit. Draw a neat phasor diagram showing I, VR, VL,Vc and V

A series circuit having pure resistance of 4022, pure inductance of 50.07mH and a capacitance is connected across a 400V, 50Hz Ac supply. This R, L, C combination draws a current of 10A. Calculate (JUN09)AUDEC10 1. Power factor of circuit 2. Capacitor value

The pressure P of a fluid is related to its number density f by the equation of state P afbf2 where a and b are constants. If the initial volume of the fluid is Vo, the work done on the system when it is compressed so as it to increase the number density from an initial value of fo to 2fo is

The input power to a 3phase a.c. motor is measured as 5kW. If the voltage and current to the motor are 400V and 8.6A respectively, determine the power factor of the system

Two wattmeters connected to a 3phase motor indicate the total power input to be 12kW. The power factor is 0.6. Determine the readings of each wattmeter. (MAY09)

Three identical coils, each of resistance 10ohm and inductance 42mH are connected (a) in star and (b) in delta to a 415V, 50 Hz, 3phase supply. Determine the total power dissipated in each case.

A Vessel has two compartments of volume V1 and V2, containing an ideal gas at pressure P1 and P2, the temperature T1 T2 respectively. If the wall seperating the compartments is removed, the resulting equilibrium temperature is

Use meshcurrent analysis to determine the current flowing in (a) the 502 resistance, and (b) the 10 resistance of the d.c. circuit shown in Figure. 49 892 302 502 6 192 13 10 5V

For the a.c. network shown in Figure determine, using meshcurrent analysis, (a) the mesh currents 11 and 12 (b) the current flowing in the capacitor, and (c) the active power delivered by the 10020 V voltage source. 100 20 V 502 HH j452 12 492 1302

Calculate current through 602 resistance using loop analysis.(AUJUNE12) 10V www ww ww www

Ten grams of Ice at 0c is added to a beaker containing 30 grams of water at 25c. what is the final temperature of the system when it comes in thermal equilibrium (The specific heat of water is calgmlc and the latent Bat Reat melting of ic is so cal 18m).

Find the current through each resistor of the circuit shown in fig, using nodal ww analysis ISV www 20V

For the a.c. network shown in Figure, determine the current flowing in each branch using Kirchhoffs laws. Z(314) 2 E (510) V 0 2g (6j8) E(214) V Z(215) 2

In the network of Figure use nodal analysis to determine (a) the voltage at nodes 1 and 2, (b) the current in the j4 2 inductance, (c) the current in the 5 2 resistance, and (d) the magnitude of the active power dissipated in the 2.5 2 resistance.(AU DEC10) 202 502 2 2.502 mont 250 V 1492 3 1402 12590 V

0.5 kg of ice at oc is added to a beaker Containing 4.5 kg of water at 20c. what is the final temperature of the system when it comes in thermal equilibrium

For the seriesparallel arrangement shown in Figure, find (a) the supply current, (b) the current flowing through each resistor and (c) the p.d. across each resistor. R60 R2.50 R20 200 V R412

A 15 mH coil is connected in series with another coil. The total inductance is 70 mH.When one of the coils is reversed, the total inductance is 30 mH.Find the self inductance of second coil, mutual inductance and coefficient of coupling.

For an ideal gas the molar heat capacity given by is CC v3aT2 where cy is independent of temperature. Find the equation of state in terms of temperature and volume

Three resistances of values 202,302 and 50 are connected in series across 20 V.D.C supply Calculate (a) equivalent resistance of the circuit (b) the total current of the circuit (c) the voltage drop across each resistor and (d) the power dissipated in each resistor.

A lamp can work on a 50 volt mains taking 2 amps. What value of the resistance must be connected in series with it so that it can be operated from 200 volt mains giving the same power.

Find the current flowing in the 4002 Resistor, R3 10v R fost R 40 (2 B V R 1092 20 (2 2 20v

An engine absorbs heat at a temperature 1000k and rejects heat at 600k. If the engine operates at maximum possible efficency, the amount of work performed by the engine, for 2000 J heat input is

A heat pump working on the Carnot cycle maintains the inside temperature of a house at 22C by suppling 450 Kjs1. If the outside temperature is 0c, the heat taken, in kJs, from the outside air is approx.

For the circuit shown in Figure 5.2, determine (a) the battery voltage V, (b) the total resistance of the circuit, and (c) the values of resistance of resistors R1, R2 and R3, given that the p.d.s across R1, R2 and R3 are 5V, 2V and 6V respectively. F R R3 4 A V V3

A 12V battery is connected in a circuit having three seriesconnected resistors having resistances of 4 2,9 2 and 11 2. Determine the current flowing through, and the p.d. across the 9 2 resistor. Find also the power dissipated in the 11 22 resistor. 492 922 1192 V 12 V

A cannot engine operates blue a heat source at 5ook and a sink at 300k. The temperature of the source is increased by 20K. In order that the efficency of the engine remaine unchanged, the temperature of the sink should be changed by

The efficency of a carnot cycle is 16. On reducing the temperature of sink by 65c the efficancy increases by 13. Find temperature of source sink

Potential divider circuits PRACTICE A lightdependent resistor (LDR) has R 25 in bright light and R 22000 2 in low light. An electronic switch will turn on a light when its p.d. is above 7.0 V. What should the value of R be 9.0 V R R N electronic switch

A filament lamp is rated at 4.0 V, 0.80 W on its package. The potentiometer has a resistance 7.0 V from X to Z of 24 2 and has linear variation. X Y R R (d) The potentiometer is adjusted so that the meter shows 4.0 V. What is the resistance of the YZ portion of the potentiometer

A cannot cycle operates as a heat engine blue two bodies of equal heat capacity until their temperature becomes equal. If the inihal temperatures of the bodies are T1 T2 respectively and T1 T2 their common final temperature is

The internal energy E(T) of a system at a fixed volume is found to depend on the temperature T as E(T) aT2bT4. Then the entropy S(T), as a fxn of temperature, is

The B.Pt. of a liquid at Pressure Po is To. Its molar latent heat of vaporisation is L and molar volume of liquid phase is negligible as compared to the vapour phase. The vapour phase obeys perfect gas equation. The B.Pt. T at Pressure P is given by

The condition for the liquid vapour phases of a fluid to be in eqm. is given by approximate eqn dpdt QtTvap If the vapour obeys ideal gas law, which is the CORRECT graph

A large number N of Brownian particles in 1Dimension start their diffusive motion from the origine at time t0. The diffusion coefficent is D. The number of particles crossing a point at a distance L from the origin, per unit time, depends on L of time t as

Let NMB, NBE, NFD denote the number of ways in which two particles can be distributed in two energy states according to maxwellBoltzmann, BoseEinstein FermiDirac statistics respectively. Then NMB MBE NFD is

Draw phase space trajectory of linear (1Dim.) Harmonic oscillator calculate number of micro state if particle has a) sharp value of energy. b) Energy lies between E to E dE.

A child makes a random walk on a square lattice of lattice constant a taking a step in the north, east, south or west direction with probabilities o.255, 0.255, 0.245, 0.245, respectively After a large number of steps, N, the expected bosition of child wirt starting point is at a distance

The partition function of two Bose particles each of which can occupy any of the two energy levels of epsilon is

The free energy of a gas. N particles in a volume V and at a temperature T is FNKBT ln ( aoV (KbT)52 N) where a is a constant of Kb denotes the bottzmann constant. The internal energy of a gas is

An atom has a nondegenerate ground state and a be doubly degenerate excited state. The energy difference between the two stater is E. The specific heat at very low temperature (BE1) is given by

For a system of independent noninteracting 1Dim oscillators, the value of the free energy per oscillator, in the limit To is

For a quantum mechanical Harmonic oscillator with energy En (n12) lembda w. The Partition fxn is

The probability of a system to be in a state with energy E at temperature T is proportional to eEKBT. If the system in question is a 1Dim. quantum H.O of frequency w the average energy at temperature T is

An airplane with its nose pointing north with an airspeed of 40 km/h in a 30-km/h crosswind (at right angles) has a groundspeed of (a) 30 km/h. (b) 40 km/h. (c) 50 km/h. (d) 60 km/h.

The team that wins in a tug-of-war is the team that (a) produces more tension in the rope than the opponent. (b) pushes hardest on the ground. (c) Both. (d) Neither

When a cannonball is fired from a cannon, both the cannonball and the cannon experience equal (a) amounts of force. (b) accelerations. (c) Both. (d) Neither

The amount of air drag on an 0.8-N flying squirrel dropping vertically at terminal velocity is (a) less than 0.8 N. (b) 0.8 N. (c) greater than 0.8 N. (d) dependent on the orientation of its body

A system has two normal modes of vibration, with frequencies w1 w2 2w1. What is the Probability that at temperature T, the system has an energy less than 4lembda w1

A 10-N force at an angle 45 above the horizontal has a horizontal component of about (a) 7 N. (b) 5 N. (c) 10 N.