• What is the flaw of this circuit analysis for obtaining the natural response?

    In this circuit and in the condition depicted, the inductance is acting as a voltage source and the resistance as a load. The + and - signs for the inductance are at the top and bottom respectively. This is, I think, exactly as stated in your question. Secondly the sum of voltages around any closed circuit is always zero. Hence L.di/dt + Ri = 0,... show more
    In this circuit and in the condition depicted, the inductance is acting as a voltage source and the resistance as a load. The + and - signs for the inductance are at the top and bottom respectively. This is, I think, exactly as stated in your question. Secondly the sum of voltages around any closed circuit is always zero. Hence L.di/dt + Ri = 0, which is according to your books and is correct. Or di/dt = -Ri/L ...... (1) The general solution to this linear, first order, differential equation is i = C.e^(-R/L).t where C is an arbitrary constant to be determined by the boundary conditions of a particular problem. Differentiate this back to check it out: di/dt = -(C.R/L).e^[(-R/L)t] which is -R/L.i, in accordance with equation (1) So everything checks mathematically. Physically perhaps your confusion is arising because the current is decaying in this circuit and di/dt is consequently negative when the current i is positive. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our modest efforts to assist.
    2 answers · Engineering · 3 weeks ago
  • Is 25 old to start studying at university and find a job or a mate?For the first time?

    Well, it's definitely time to get your act together and begin to shoulder some real responsibility for yourself, your family and your community. That's the only route to a full and satisfying life. Every human is destined to carry a load, so pick up the biggest one you can lift and get moving.
    Well, it's definitely time to get your act together and begin to shoulder some real responsibility for yourself, your family and your community. That's the only route to a full and satisfying life. Every human is destined to carry a load, so pick up the biggest one you can lift and get moving.
    7 answers · Engineering · 4 weeks ago
  • What is the stored Energy in AC capacitor - AC or DC ?

    The energy (E) stored in a capacitor depends on the capacitance (C) and the voltage (V) across the capacitor. It is always given by ½.C.V². So if the applied voltage is alternating (at angular frequency ω) and we write it as V.sin ωt then the stored energy at any time (t) after the voltage is applied and stationary conditions have been attained,... show more
    The energy (E) stored in a capacitor depends on the capacitance (C) and the voltage (V) across the capacitor. It is always given by ½.C.V². So if the applied voltage is alternating (at angular frequency ω) and we write it as V.sin ωt then the stored energy at any time (t) after the voltage is applied and stationary conditions have been attained, is: E = ½.C.V².sin²(ωt) So the energy stored on the capacitor goes up and down again twice per ac cycle but is always between 0 and a positive value. So it has a direct component and a component alternating at 2ω since sin²(ωt) = 1-cos(2.ωt). Fill in your values if you need a numerical result. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist.
    9 answers · Engineering · 4 months ago
  • Find a possible formula for P=f(t), where t is time in minutes. Assume there is no phase shift.?

    Mean pressure over time = (232+100)/2 = 166. Amplitude of oscillating component if we assume it to be sinusoidal = (232-100)/2 = 132/2 = 66. Period of oscillation = 10 mins therefore frequency = f = 0.1 /min. and angular frequency = ω = 2.π.f = 0.2×π where × is the multiplication sign. The oscillation is at a minimum at t=0 and is best... show more
    Mean pressure over time = (232+100)/2 = 166. Amplitude of oscillating component if we assume it to be sinusoidal = (232-100)/2 = 132/2 = 66. Period of oscillation = 10 mins therefore frequency = f = 0.1 /min. and angular frequency = ω = 2.π.f = 0.2×π where × is the multiplication sign. The oscillation is at a minimum at t=0 and is best represented in the form = -cos(0.2×π).t Giving the final expression: P = 166 - 66.cos(0.2×π×t) Please award one of your responses "Best Answer". We particularly appreciate this small token of recognition for our modest efforts to assist.
    3 answers · Engineering · 1 year ago
  • How to calculate a non-steady state heat exchange between a heat source and a steady flow of cold water.?

    Best answer: Let the temperature of the water leaving the pipe be T. This is a function of time t which we measure in minutes. Let the temperature of water in the tank be θ. This is also a function of t. How I tackle this problem depends strongly on how I interpret your term "efficiency of the heat exchanger". If the... show more
    Best answer: Let the temperature of the water leaving the pipe be T. This is a function of time t which we measure in minutes. Let the temperature of water in the tank be θ. This is also a function of t. How I tackle this problem depends strongly on how I interpret your term "efficiency of the heat exchanger". If the "performance" (I think efficiency is an inappropriate term) of the heat exchanger were to be 100% then I'd understand that the water leaving bthe pipe would always be at T=θ which means that its temperature rise would be (θ – 10). I assume that "50% heat exchanger efficiency" means that the temperature rise of the water leaving the pipe is 50% of that value, i.e. ΔT= 0.5×(θ-10) giving: T=0.5×(θ-10)+10 = 0.5×θ+5 = 0.5×(θ+10) ......... (A) This means that the water initially (t=0) leaves the pipe at T(0) = 30˚C Now the rate of heat loss by the tank water is equal to the heat-flow rate in the pipe water i.e.: dθ/dt = -ΔT×10/100 ˚C /min. or: dθ/dt = -0.5×(θ-10)/10 or dθ/dt = 0.5 - 0.05θ Solving this linear, separable, first-order, differential equation gives the general solution: θ(t) = C.e^(-0.05t) + 10 where C is an arbitrary constant to be determined by the boundary conditions. obviously, to give θ(0) = 50, C must = 40 giving the particular solution for this problem as: θ(t) = 40.e^(-0.05t) + 10. Enter t = 10 into this formula and get the final value of θ = θ(10) Energy lost by water in 10 min = 100×[50-θ(10)]×s where s is the specific heat of water in J/kg/˚C. The final temperature of the water emerging from the pipe is found by entering θ(10) in any of the formulae A. I think you must be able easily to handle the substitutions and arithmetic. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    2 answers · Engineering · 1 year ago
  • Can you help me with Physics?

    Best answer: Yes you're spot on! Note however that food Calories are already kilocalories, so in terms of food labelling and nutritional discussion, 4.4 Calories would be used. Thus food Calories (commonly written with a capital in an attempt to avoid confusion!) are kilocalories You're also correct in multiplying by 4 to account for the 25%... show more
    Best answer: Yes you're spot on! Note however that food Calories are already kilocalories, so in terms of food labelling and nutritional discussion, 4.4 Calories would be used. Thus food Calories (commonly written with a capital in an attempt to avoid confusion!) are kilocalories You're also correct in multiplying by 4 to account for the 25% efficiency. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    2 answers · Engineering · 1 year ago
  • Advantages and disadvantages for repeat purchase?

    Repeated purchase should, in itself, allow you to open negotiations for a better price. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    Repeated purchase should, in itself, allow you to open negotiations for a better price. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    2 answers · Engineering · 1 year ago
  • Where to order thin metal plates? ( For a project - approximately 1" x 2.5" x 0.075" )?

    You should find them easily on Ebay but you'd do well to know and to specify which metal. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    You should find them easily on Ebay but you'd do well to know and to specify which metal. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    3 answers · Engineering · 1 year ago
  • How much does a rotor of a very large turbine generator weigh )ball park)?

    Best answer: The largest steam driven turbogenerators are four pole 1800 rpm units used in large nuclear plants. Their rotors weigh around 200 metric tons. Large multi-pole generators for hydro-plants can be even heavier. They may need to be assembled on site. Manufacturers are GE, Siemens and possibly Mitsubishi. Formerly they were also built by... show more
    Best answer: The largest steam driven turbogenerators are four pole 1800 rpm units used in large nuclear plants. Their rotors weigh around 200 metric tons. Large multi-pole generators for hydro-plants can be even heavier. They may need to be assembled on site. Manufacturers are GE, Siemens and possibly Mitsubishi. Formerly they were also built by ABB, Brown Boveri and Westinghouse but these names are now out of the business. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    6 answers · Engineering · 1 year ago
  • Dynamics problem: In the cam-follower mechanism (shown in figure below), the slotted bar rotates with constant angular velocity w=20rad/s...?

    Best answer: r = 2+0.75cos(2θ) = 2+0.75×cos(2.ω.t) = 2 + 0.75×cos(40.t) θ = ω.t = 20.t radial acceleration = a = d²r/dt² - ω².r = -0.75×40×40×cos(40.t) - 20×20×[2 + 0.75×cos(40.t)] ...... (1) At θ = π/4, t = π/80 s. Plug t= π/80 into 1 to get the answer for the radial acceleration A at θ = 45˚ = π/4.. There is conveniently no angular acceleration so... show more
    Best answer: r = 2+0.75cos(2θ) = 2+0.75×cos(2.ω.t) = 2 + 0.75×cos(40.t) θ = ω.t = 20.t radial acceleration = a = d²r/dt² - ω².r = -0.75×40×40×cos(40.t) - 20×20×[2 + 0.75×cos(40.t)] ...... (1) At θ = π/4, t = π/80 s. Plug t= π/80 into 1 to get the answer for the radial acceleration A at θ = 45˚ = π/4.. There is conveniently no angular acceleration so the x and y components of acceleration at θ = π/4 are each A/(√2). I let you crunch the numbers! Please award one of your responses Best Answer. We especially value this particular small recognition of our modest efforts to assist
    1 answer · Engineering · 1 year ago
  • Where will I get a time machine?

    Best answer: Any watch or clock shop the choice depending upon how much importance you attach to portability. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    Best answer: Any watch or clock shop the choice depending upon how much importance you attach to portability. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    4 answers · Engineering · 2 years ago
  • Science question:True or False?

    Best answer: 1) It does not become heavier but it will stop rising because the air outside it becomes less dense. So F & T. 2) T 3) T 4) F (if you mean fluid's speed and not speed's fluid) 5) F 6) T Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to... show more
    Best answer: 1) It does not become heavier but it will stop rising because the air outside it becomes less dense. So F & T. 2) T 3) T 4) F (if you mean fluid's speed and not speed's fluid) 5) F 6) T Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist.
    1 answer · Engineering · 2 years ago
  • EE alternators/transformer?

    Running at 25 MVA the first generator is severely overloaded since its rating is only 20 MVA. The situation is not sustainable
    Running at 25 MVA the first generator is severely overloaded since its rating is only 20 MVA. The situation is not sustainable
    2 answers · Engineering · 2 years ago
  • Why the resistance in dc distribution system for the length of 100 meters(length of distributer) is assumed as r/2?

    Best answer: If something is an assumption then it is not open to question. It is already assumed. You cannot ask "why" unless the assumption conflicts with other given conditions of which you do not provide any. All of your other answers create such a conflict by also assuming two (one go and one return) conductors in series which gives... show more
    Best answer: If something is an assumption then it is not open to question. It is already assumed. You cannot ask "why" unless the assumption conflicts with other given conditions of which you do not provide any. All of your other answers create such a conflict by also assuming two (one go and one return) conductors in series which gives 2r but you do not specify that. A valid implication of your assumption may be that r = the resistance of 400 m of conductor. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist.
    5 answers · Engineering · 2 years ago
  • Compute for the effective value of a voltage with a maximum value of 325 volts.?

    Assuming the voltage to be ac having a sinusoidal waveform, the effective value = 325/√2 ≈ 229.8 or, in practical terms, 230 volts. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist.
    Assuming the voltage to be ac having a sinusoidal waveform, the effective value = 325/√2 ≈ 229.8 or, in practical terms, 230 volts. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist.
    2 answers · Engineering · 2 years ago
  • Safe to put lower watt bulb in socket?

    If both the 60 and 75 W bulbs have the same rated voltage and the supply voltage does not exceed that value, then it's perfectly OK. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    If both the 60 and 75 W bulbs have the same rated voltage and the supply voltage does not exceed that value, then it's perfectly OK. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    6 answers · Engineering · 2 years ago
  • Is it possible to have dilatation without internal stress?

    Best answer: Yes you can have expansion caused by heating (thermal expansion) but if, for example, the temperature is kept unifoirm throughout the body during the heating process, then there might well be no internal stress. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our... show more
    Best answer: Yes you can have expansion caused by heating (thermal expansion) but if, for example, the temperature is kept unifoirm throughout the body during the heating process, then there might well be no internal stress. Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    1 answer · Engineering · 1 year ago
  • Can anyone help me answer this problem on position analysis?

    Best answer: Where I am located it's a bit too late for me to write all this out tonight. I shall do it tomorrow. Do you award Best Answer if you get a good one? The clue is in triangle O₂ O₄ A which will have a max deflection to the left when its angle at 3 is 90 degrees and also to the right under that same condition. The said triangle is... show more
    Best answer: Where I am located it's a bit too late for me to write all this out tonight. I shall do it tomorrow. Do you award Best Answer if you get a good one? The clue is in triangle O₂ O₄ A which will have a max deflection to the left when its angle at 3 is 90 degrees and also to the right under that same condition. The said triangle is then a 3, 4, 5, making the angle to the vertical at O₄ equal to arccos(4/5) and therefore the total angular range of 4 = 2.arccos(4/5) = 73.74 degrees The slider stroke is then easy. Let me know meanwhile if you still can't do it. Slider stroke is then the horizontal distance moved by B = 2.O₂B.sin[arccos(4/5)] = 4 x 0.6 = 2.4 cm. Please don't forget the Best Answer award !! Thank you.
    1 answer · Engineering · 1 year ago
  • What is electricity ?

    Quite generally, electricity is either the movement of electrons or their presence or absence in excess, so as to provide a net negative or positive charge. It works in many different ways: magnetism, electromagnetic radiation, energy transmission, induction, electrolysis, etc..... Please award one of your answers "Best Answer". We... show more
    Quite generally, electricity is either the movement of electrons or their presence or absence in excess, so as to provide a net negative or positive charge. It works in many different ways: magnetism, electromagnetic radiation, energy transmission, induction, electrolysis, etc..... Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    4 answers · Engineering · 2 years ago
  • Multivariable calculus help PLEASE?

    Best answer: i = V/R Using differentiation of a quotient we obtain: di/dt = [R.dV/dt-V.dR/dt]/R² = [-2 - 1×0.01]/10⁴ = - 20.1×10⁻³ A/s Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    Best answer: i = V/R Using differentiation of a quotient we obtain: di/dt = [R.dV/dt-V.dR/dt]/R² = [-2 - 1×0.01]/10⁴ = - 20.1×10⁻³ A/s Please award one of your answers "Best Answer". We especially appreciate this particular small recognition of our efforts to assist
    1 answer · Engineering · 2 years ago