(DEC 11) B. Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) ELECTRONICS & COMMUNICATIONS Paper - I : Mathematics - III Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory (15 1 = 15) Answer ONE question from each unit (4 15 = 60) 1) a) Write the Euler s notations. b) Define odd function c) Define fourier integral theorem. d) Define cosine series of f(x) e) Define inverse fourier transform. f) Show that E = E. g) Define differential operator. h) Newton forward interpolation formula i) Write Gauss Interpolation formula. j) Write striling Interpolation formula. k) Write taylor s series method. l) Write the formula for trapezoidal rule. m) Write formula s 4 th order R-k method.
n) Write Euler s method formulas. o) Write diveded difference formula. UNIT - I ) a) Find the fourier series of the function. f(x) = x, x < Hence deduce that : i) ii) iii) 1 1 1 1 6 1 3 4 1 1 1 1 1 1 3 4 1 1 1 8 1 3 5......... b) Find the fourier series to represent x x, < x <. Hence deduce that 1 1 1... 1 3 5 8 c) Find the fourier series to represent the f(x) f(x) = 1 for < x < = for < x < and Hence deduce that 1 1 1 1... 4 3 5 7 UNIT II 3) a) Write a modulation property of fourier transform. b) Find the fourier transform of f(x) where f(x) is defined by and equation 0 sin p dp p c) Find the root of the equation e x sin x = 1 by regula falsi method. d) Write procedure to solve system of linear equations by Gauss elimination method.
UNIT III 4) a) Find a cubic polynomial for the data given below. 1. x. 0 3. 1 4. 5. 3 6. f(x) 7. 1 8. 3 9. 7 10. 13 b) Using lagrange s formula find Y35 given that Y0 = 51, Y30 = 439, Y40 = 346, Y50 = 43. c) Given Find using interpolation formula. d) Give the values : 11. x 1. 5 13. 7 14. 11 15. 13 16. 17 17. f(x) 18. 150 19. 39 0. 145 1. 366. 50 Find f(9) using Newton diveded difference formula. UNIT - IV 5) a) Find the value 1 dx 1 x 0 rules correct to five significant figures. taking 5 subinterval by trapezoidal, simpson s 1 3 simpson s 3/8th b) Find an approximate value of y for x = 0.1, 0., 0.3 by Picard s method given dy y x that, y (0) 1 dx y x
(DEC 1) B. Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) ELECTRONICS & COMMUNICATIONS Paper - II : Circuit Theory Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory (10 1½ = 15) Answer ONE question from each unit (4 15 = 60) 1) a) Define ideal Elements. b) Units of & G. c) Define power. d) Write about KCL. e) Difference b/w mesh and nodal Analysis f) Relation b/w power, voltage & Current. g) State Reciprocity theorem. h) AVG and RMS value of sinusoidal waveforms. i) Relation b/w Bandwidth and Q Factor. j) Advantages of three phase system. UNIT - I ) a) Explain about the star to delta & delta to star. b) Find the R3 value.
3) a) Write about mesh analysis of circuits excited by independent and dependent sources. b) Solve the mesh currents of the circuits shown in fig. UNIT II 4) a) State and prove the superposition theorem. b) Find the current in the 5 resistor of given fig. using superposition theorem. 5) Determine the Theviniens & Nortons equivalent of the circuits shown in fig. 1 with respect to terminals A & B. UNIT III 6) Calculate the response of R, L ic series and parallel. Combination circuits to sinusoidal excitation. 7) Explain about Series Resonance and derive the expression for resonant frequency & quality factor.
UNIT IV 8) What is poly phase system & Explain its advantages and disadvantages. Explain its operation for 3phase sources and loads. 9) In the RLC circuit of fig. the capacitor has an initial voltage of 40v, when the switch is closed at t = 0. Find an expression for the current i(t)
(DEC 13) B. Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) Electronics & Communications Paper - III : ELECTRONIC DEVICES Time : 3 Hours Maximum Marks : 75 Answer question No. 1 compulsory (15 x 1 = 15) Answer ONE question from each unit (4 x 15 = 60) 1) a) Define mass action law. b) What is the difference between p-n diode and zener diode? c) What is intrinsic semiconductor. d) What are the applications of CRO. e) What is meant by depletion region. f) Define carrier life time. g) What are the applications of LED. h) What is negative temperature coefficient of temperature? i) Draw the PNP common collector transistor configuration. j) What is Diffusion capacitance? k) What are the applications of diode? l) What is Base width modulation? m) Define transport factor, in a transistor.
n) Why FET is called unipolar device? o) What is meant by pinch off voltage in FET. Unit I ) a) Give the constructional details of cathode ray tube. b) What is drif current? 3) a) Draw the block diagram of CRO and explain function of each block. b) In a CRT, a pair of deflecting plates all cm long and are spaced 0.5cm apart. The distance from the center of the plates to the screen is 4 cm. The final node voltage is 1000V. Calculate the displacement produced by deflecting voltage of 30V. Unit II 4) a) Derive PN junction diode equation. b) Calculate the factor by which the current will increase in silicon diode operating at a forward voltage of 0.4 volts. When the temperature of raised from 5 C to 150 C. 5) a) Compare Avalanche and zener break down mechanisms. b) Explain how zener diode works as voltage regulator. Unit III 6) a) Explain the current components in transistor with a neat diagram. b) Explain how the transistor acts as an amplifier. 7) a) Explain the characteristics of transistor in CB configuration. b) Derive the relationship between, and
Unit IV 8) a) Explain the characteristics of JFET. b) Explain the classification of field effect transistors. 9) a) Explain the construction and operation of UJT. b) Give the UJT symbol and simplified equivalent circuit with external resistors included.
(DEC 14) B. Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the End of Second Year) ELECTRONICS & COMMUNICATIONS Paper - IV : EMF Theory Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory Answer ONE question from each unit (4 15 = 60) 1) a) State Coulombs law. (1) b) Write down the of Poisson s equations in a non-homogeneous and homogeneous region? () c) Explain the concept of Skin Depth. () d) State Ampere s circuital law and obtain third Maxwell s equation. () e) Does an isolated magnetic charge exists? Justify. () f) State curl s theorem. (1) g) Express divergence of electric field in integral form. (1) h) Find direction of propagation for the field E = 50 cos (10 8 t z) a v V/m. (1) i) Define polarization. (1) j) State Poynting s Theorem. (1) k) Express magnetic scalar potential. (1) UNIT - I ) a) Derive the electric flux density for a surface charge using coulomb s law with relevant coordinate system. (8) b) i) Prove. D = v. ii) A point charge 100 pc is located at (4, 1, 3) while the x-axis carries charge nc/m. If the plane z = 3 also carries 5 nc/m. Find E at (1, 1, 1). (7)
3) a) Derive the expression for a capacitance of coaxial capacitor with neat schematic. (8) b) Derive the expression for energy stored in electrostatic fields. (7) UNIT II 4) a) State and derive Biot-Savart s law. Is Magnetostatic field conservative, explain and obtain M.E of divergence of magnetic field. (10) b) A steady state current of I amps flow in a conductor bent in the form of square loop of side a. Find the H at the center of the loop. (5) 5) a) Derive the expression of H for surface current distribution with neat schematic? (10) b) Determine i) J d and ii) H for E = 0 cos ( t-50z) a y V/m in free space. (5) UNIT - III 6) a) Derive expression for a force between two current elements. A current element of length cm is located at the origin in free space and carries current 1ma along a z, A filamentary current of 15 a z A is located along x = 3, y = 4. Find the force on a current filament. (10) b) Derive relaxation time. (5) 7) a) Explain how the transformer emf and motional emf are produced. (8) b) Derive law of refraction of the electric field at a boundary form Maxwell s equations. (7) UNIT IV 8) a) Derive the expressions of E & H for a lossy medium. (10) b) A plane wave travelling in the +y direction in a lossy medium characterized by r = 4, r = 1, = 10 mhos/m has E = 30 cos (10 9 t + ( /4) a z V/m at y = 0. (5) Find i) E at y = 1m and t = ns ii) H at y = m and t = ns.
9) a) Derive Poynting s Theorem using Maxwell s equations. (8) b) In a non-magnetic medium = 4 sin ( 10 7 t 0.8x) a z V/m. find (7) i) relative permittivity and ii) time average power carried by the wave iii) the total power crossing 100 cm of plate x + y = 5.
(DEC 15) B. Tech DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) Electronics & Communications Paper - V : DIGITAL ELECTRONICS Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory (15 1 = 15) Answer ONE question from each unit (4 15 = 60) 1) a) What is meant by radix (base) of number system? b) What is Excess-3 code? c) What is meant by weighted number system? d) Explain about race-around condition & How to avoid it? e) Which logic gate is used to compare the I/PS? f) Express the function in y A+ BC in canonical sop form. g) What are the universal gates & why they are called universal gates. h) How many Half adders are used to construct full adder. i) What is difference between combinational circuit & sequential circuit. j) What does ECC stands for? k) List the applications of shift register. l) (ECE) 16 convert into Decimal number. m) (1001101) convert into Gray code.
n) Which code is called as self complementary code? Explain with example. o) What is decoder? UNIT - I ) a) Convert the (73) 10 into Binary, octal & Hexadecimal form. b) Perform subtraction operation on 68 48 using complement subtraction method. 3) a) Simplify the Boolean function by using K map F = m (0, 1,, 5,7, 9,1, 13, 15) b) Simplify the given Boolean function by using tabulation method F = m (1,, 3, 5, 6, 7, 8, 9,1, 13, 15) UNIT II 4) a) Draw & Explain the operation of 4 bit parallel Adder. b) Differences between serial adder & parallel adder. 5) a) Design Encoder logic diagram to convert decimal number into Binary number. b) What is multiplexer? Draw & explain the operation of 8:1 mux. UNIT - III 6) a) Explain the operation & Truth table of SR NAND latch. b) Explain the operation of JK flip flop. 7) a) Design MOD 10 Asynchronous counter using JK flip-flop & Draw o/p waveforms. b) Difference between synchronous & Asynchronous counters.
UNIT IV 8) a) Draw the PAL circuit to implement the logic functions listed below. A (x, y, z) = (1,, 3, 4) B (x, y, z) = (0, 1, 6, 7) C (x, y, z) = (, 6) D (x, y, z) = (1,, 3, 5, 7) b) Discuss the comparision between PROM, PLA, PAL. 9) Briefly Explain about the following logic families a) RTL b) DTL c) TTL d) ECL
(DEC 16) B. Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) ELECTRONICS & COMMUNICATIONS Paper - VI : Data Structures Using C Time : 3 Hours Maximum Marks : 75 Answer question No. 1 compulsory (15 x 1 = 15) Answer ONE question from each unit (4 x 15 = 60) 1) Write short notes on : a) Bubble sort b) Queues c) Linear Search d) B-Tree e) Stack applications Unit I ) Write a suitable program to explain the list operations and their implementation using arrays. 3) Explain : a) Single linked list b) Double linked list Unit II 4) Write a program to show the implementation of a stack using linked list. 5) Explain the applications of a Queue.
Unit III 6) Discuss Quick Sort with example. 7) Differentiate selection sort and insertion sort. Unit IV 8) Explain the hashing methods and applications. 9) Explain in detail about AVL-Trees.
(DEC 1) B. Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) ELECTRONICS & COMMUNICATIONS Paper - I : Mathematics - IV Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory (15) Answer ONE question from each unit (4 15 = 60) 1) a) Define entire function. b) Define Cauchy Riemann equation in Cartesian form. c) Define orthogonal system. d) Define Taylor s series. e) Define Bessel s equation. f) Define Legendre s equation. g) Define frobenius method. h) Define Removable singularity. i) Define Residue theorem. j) Find the Residue of 1 f ( z) at z 1 ( z 1)( z 3) k) Define pole. l) Write expression for p 3 (x). m) Write orthogonal property of Legendre polynomial.
n) Define conjugate of a function. o) Define zero s of a function. UNIT - I ) a) State and prove Riemann equation for polar coordinates. b) Show that f(z) = xy + iy is every where continuous but is not analytic. 3) a) If w = log z find and determine where w is non analytic. b) Find the orthogonal trajectories of family of curve x 4 6x y + y 4 = C. UNIT II 4) a) Find the Taylor s serie s expansion of f() z z 9z 5 3 z z z 8 1 about z 0 = 1. z 4 b) Compute dz where c is z+1 - i = z z 5 c 5) a) State and prove taylor s series. b) Find the taylors series expansion of f() z z 9z 5 3 z z z. 8 1 UNIT - III 6) a) State and prove Residue theorem. b) Show that cos a d ( a 1) 1 a cos a 1 a 0. 7) a) Prove that 0 a d cos a 1 a 1 b) Solve the series in equation y xy y 0.
UNIT IV 8) a) d Prove that x n J n n( x ) x J n 1( x ). dx b) P.T. Pn ( x) xpn 1( x) npn 1( x ). d 9) a) Prove that x J 1( x ) x J 0( x ). dx b) Show that 1 1 xp ( x) p x dx n n 1 n. 4n 1
(DEC ) B. Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) ELECTRONICS & COMMUNICATIONS Paper - II : Electronic Circuits - I Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory Answer ONE question from each unit 1) a) Define miller s theorem b) Why h- parameter are not suitable at high frequencies? c) What are the applications rectifiers? d) List out characteristics of Darlington pair. e) What are advantages of RC coupling in multistage amplifier? f) List out characteristics of CS amplifier g) Compare BJT and FET amplifiers h) What is effect of bypass capacitor in CE amplifiers? i) Define Harmonic distortion UNIT-I ) a) Explain the operation of center tapped FWR. with circuit and necessary waveforms b) Design a filter for FWR circuit with LC filter to provide an output voltage of 10 volts with a load current of 00 ma and the ripple is limited to % 3) a) With circuit and necessary waveforms explain the operation of Bridge Rectifier
b) In a Bridge rectifier, the transformer is connected to 0 volts, 60 Hz mains and turns ratio of the step down transformer is 11:1. Assuming the diodes to be ideal, find i) voltage across the load ii) D.C current iii) PIV. UNIT II 4) a) Classify different types of amplifiers? b) The h-parameters of a CE amplifier are hie = 1100, h fe =50, hre =.5X 10 4, h oe = 4 A/V and R s = 1k and R L = l0k. Find the current and voltage gain, (with and without source resistance) input & output impedances 5) a) Explain in detail different types of distortions in amplifier. b) Compare CE,CC and CB amplifier. UNIT-III 6) a) Describe the emitter follower at high frequency and also derive the equation for higher cutoff frequency b) Write Short note Gain Bandwidth product 7) a) Define and explain terms f and f T. b) Derive the expression for CE short circuit current gain and explain the significance of f T in hybrid model. UNIT-IV 8) a) Draw the circuit diagram of cascade amplifier and derive its overall voltage gain and Input impedance from its equivalent circuit. b) Discuss different coupling methods used in multistage amplifier 9) a) Explain the small signal MOSFET circuit model. b) Draw and explain the CS amplifier with current source load.
(DEC 3) B.Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) ELECTRONICS & COMMUNICATIONS Paper - III : Transmission Lines & Waves Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory (15m) Answer ONE question from each unit (4 15 = 60m) 1) a) State one difference b/w attenuation constant & phase constant. b) Define Group velocity. c) Define standing wave ratio. d) Applications of single stub. e) Mathematical expression for velocity of propagation. f) What is double stub matching? g) Give the characteristics of TE Wave. h) Write the expressions for Attenuation factor & Q-factor? i) What is symmetrical strip transmission? j) Which is dominant mode in circular wave guide? UNIT - I ) a) Define and derive the expression s for attenuation & phase constant. b) A telephone wire 10 km long has the following constants per loop km resistance 50, capacitance 0.01 F, inductance 0.001 H and leakage = 1.5 10-6 mhos. The line is terminated in its characteristics impedance and potential difference of V having a frequency of 000 Hz is applied at Sending end. Calculate velocity of propagation and wave length.
3) Write short notes on a) Velocity of propagation. b) Group velocity c) Waveform distortion d) Reflection coefficient. UNIT - II 4) a) Differentiate b/w single stub and double stub Impedance matching. b) List out the various parameters of co-axial lines at high frequencies. 5) A transmission line of length & characteristic impedance 0.4, 100 respectively and is terminated with a load impedance of 100 + j 90. Find the (i) Voltage reflection coefficient (ii) VSWR (iii) Input Impedance of the line. Compare the results with Smith Chart. UNIT - III 6) a) Compare the transverse electric waves versus Transverse magnetic waves. b) Explain about the dominant & other important modes. 7) Explain the concept of impossibility of TEM and also Derive an expression for it? UNIT - IV 8) Give the solutions to the field equations in cylindrical co-ordinates. 9) a) Explain briefly about parallel plate transmission. b) Differentiate Symmetrical Strip transmission & Assymmetric Strip transmission.
(DEC 4) B. Tech DEGREE EXAMINATION, MAY - 015 (Examination at the End of Second Year) Electronics & Communications Paper - IV : NETWK ANALYSIS & SYNTHESIS Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory (10 1½ = 15) Answer ONE question from each unit (4 15 = 60) 1) a) What is a Lattice network? b) What is an attenuator? c) What is meant by open circuit impedance? d) What is filter? e) Define attenuator. f) Define Equalizer. g) What is meant by Positive real functions? h) What is meant by Reactance functions? i) Expression for constant K. high pass filter. j) Define pass and stop bands. UNIT - I ) Explain the network functions for the one part and two parts with an example. 3) a) Explain the Open Circuit Impedance and Short Circuit admittance for Two part networks. b) Obtain the Relation b/w parameter sets.
UNIT - II 4) a) Define filter and explain about the characteristics impedance of symmetrical n/w s. b) Explain the properties of symmetrical n/w s. 5) a) Derive the expression for Constant K. low pass filter. b) Derive the O/P expression for m-derived T-section filter. UNIT - III 6) a) Describe the concept of symmetrical & Asymmetrical auenuators. b) Write short notes on i) Latice attenuator ii) Bridged T attenuator 7) a) Explain the configuration of equalizer. b) Comparision b/w Bridged T equalizer & Lattice equalizer. UNIT - IV 8) a) Explain the concept of positive real functions and Reactance functions. b) Explain about the RC & RL functions. 9) Explain in detail about FOSTER and CAUER methods of synthesis.
(DEC 5) B.Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) ELECTRONICS & COMMUNICATIONS Paper - V : Electrical Technology Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory (15) Answer ONE question from each unit (4 15 = 60) 1) a) Write the main parts in 1- Transformer b) What is the principle of operation of 1- Transformer. c) What are the constructional details of DC Generator. d) Explain about Armature reaction in DC Generator. e) Draw the characteristics of DC Shunt Generator. f) What is the purpose of starter. g) Write the applications of DC series motor. h) Draw the Torque-slip characteristics of Induction motor. i) Which type of slots are used in Induction motor. j) Which type of materials are used for Commutator Brushes? k) Write any one difference between Induction motor and 1- Transformer. l) What is the purpose of Damper winding. m) Write the applications of stepper motors. n) Draw the circuit diagram of Auto Transformer. o) What are the losses are presented in Induction motor.
UNIT I ) a) How emf is generated in DC Generators. Derive emf equation in a DC Generator. b) Explain Load characteristics of DC series Generator. 3) a) Derive Torque equation in DC motor. b) Explain 3-point starter with neat sketch. UNIT - II 4) a) Explain 1- Transformer operation with no-load. b) Explain about 3- Transformers. 5) a) Explain OC and SC Test in a 1- Transformer. b) 1- Two winding transformer operated with 0KVA and 000/00V. If the two winding transformer is converted into Auto transformer. What is the capacity of Auto transformer? UNIT - III 6) a) Explain concept of rotating magnetic field in Induction motors. b) A 3-, 50Hz Induction motor has a full load speed of 1440 rpm. For this speed calculate the following (Rated speed is 1500 rpm) (i) No. of poles (ii) Full load slip (iii) Rotor frequency. 7) a) Derive the condition for maximum torque in Induction motors. b) Explain about stepper motors. UNIT - IV 8) a) Explain principle of operation of synchronous machine. b) Derive EMF equation in synchronous machines. 9) a) Explain about synchronous Impedance method. b) Write the applications of synchronous machines.
(DEC 6) B.Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the End of Second Year) ELECTRONICS & COMMUNICATIONS Paper - VI : Signals & Systems Time : 3 Hours Maximum Marks : 75 1) Write briefly on : Answer question No.1 compulsory (15) Answer ONE question from each unit (4 15 = 60) a) What is aliasing effect. b) What are the properties of correlation function. c) Define Sample Space & Event. d) Give short notes on Mean Ergodic processes. e) Distinguish between auto correlation & cross correlation. f) What is equally likely event. g) What is the importance of sampling theorem. h) Find the signal band width of cos 100 t + cos 00 t. UNIT I ) a) State & prove sampling theorem for band limited signals. b) Check whether the following signals are orthogonal (or) not. X ( n) 1 e jk 8 n X ( n) e jm 8 n
3) a) Consider the periodic square wave x(t) as shown in figure below. Determine the complex exponential Fourier series of x(t). b) State & prove the properties of Fourier transform. i) Time shifting ii) Time scaling UNIT - II 4) a) What is Paley winer criterion? Explain its significance. b) Verify parseval s theorem for the energy signal. x(t) =.e -t. u(-t) 5) a) Discuss power density spectrum properties. b) Give short notes on convolution, stability & causality. UNIT - III 6) a) The antenna is having temperature 30º K is connected to the input of receiver equivalent input noise temperature is 70ºK. The mid band available power gain is 10 10. The noise band-width is 1.5 mhz. Find out the available out put noise power. b) Derive the expression for the noise figure in terms of the input & output signal-to noise ratios. 7) Write short notes on a) Thermal noise. b) White noise. c) Amplifier noise. d) Upon what factors does the noise voltage depend? e) Noise figure.
UNIT - IV 8) a) Let x be a random variable with distribution f x given by f x ( x) x 1 e, 0 x 0, otherwise Find the pdf of x. Determine the mean & variance of the distribution. b) State & prove the Baye s theorem. 9) a) A random process X(t) is applied to a system whose impulse response is h( t) 3.4( t) t exp ( 8 t ) If E[X(t)] =, what is the mean value of the system response y(t). b) Give short notes on Average noise figure.
(DEC / DME / DCE 7) B.Tech. DEGREE EXAMINATION, MAY - 015 (Examination at the end of Second Year) ELECTRONICS & COMMUNICATION AND MECHANICAL AND CIVIL ENGINEERING Paper - VII : Environmental Science Time : 3 Hours Maximum Marks : 75 Answer question No.1 compulsory (15) Answer any ONE question from each unit (4 15 = 60) 1) Write short notes on : a) Modern agriculture. b) Renewable resources. c) Food web. d) Earth quake. e) Endemic species. UNIT I ) Discuss the scope of environmental studies with respect to the following statements. a) Our dependence on nature is so great that we cannot live without protecting earth s environment. b) Industrial development affects the environment. 3) Discuss uses and over exploitation of mineral Resources.
UNIT - II 4) What do you understand by energy flow in an ecosystem? 5) Discuss the following: a) Habitat loss b) Poaching of wild life c) Hot spots of Biodiversity UNIT - III 6) Write a short notes on a) Noise pollution. b) Soil pollution. 7) How can you, as an individual, prevent Environmental pollution? UNIT - IV 8) Discuss various measures from unsustainable to sustainable development? 9) Discuss about the a) Resettlement and rehabilitation of People. b) Urban Problems related to energy.