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  1. R

    A circuit problem

    I believe he already has the solution here. http://www.electro-tech-online.com/threads/a-circuit-problem.146460/ Ratch
  2. R

    Better understanding of Electricity.

    Current needs a conduction path, but that is not what I am gripping about. Didn't I make it clear that current is charge flow? Therefore current flow literally means charge flow flow. What is there about that phrase current flow that you don't understand? Ratch
  3. R

    Better understanding of Electricity.

    First, he is wrong from the start. Ohm's law in not V=IR and all its variations. R=V/I is the definition of resistance, not Ohm's law. Ohm's law is the electrical linearity of a material. It is a property of a material, not a definition or method of determining V,I, or R. The definition...
  4. R

    Energy Lost Due To Friction

    Then how will knowing the speed at the end of the descent help find the changing friction during the descent of the incline? Anyway, I believe the problem assumes a constant frictional force. In that case, the acceleration will be constant, but less than it would be if not friction were...
  5. R

    Energy Lost Due To Friction

    OK, I see what you mean now. Yes, that will work. I used the increase in time caused by the friction to compute the reduction in acceleration. Then multiply by the mass of the trolley to get the friction directly without computing any potential energy or kinetic energies. Ratch
  6. R

    Energy Lost Due To Friction

    Not true, he did not explain how to get the instantaneous speed at the bottom of the incline other than the difficult task of direct velocity measurement. There is a better way. Can you find it? Ratch
  7. R

    Energy Lost Due To Friction

    If the friction component is so small that it would not slow down the trolley, and not cause it to take longer to descend the incline, would it not be too small to measure with a scale? Besides, the problem specifies that the friction be found from the trolley's descent down an incline, not a...
  8. R

    Energy Lost Due To Friction

    But that's irrelevant. You need the instantaneous speed at the bottom of the incline, not the average speed to compute the kinetic energy. Ratch
  9. R

    Energy Lost Due To Friction

    Afraid not. For constant acceleration, speed doubles as the square of the distance. That means that the speed at the end of the incline will be sqrt(2) or 1.414... of what it was half-way down the incline. Measuring the speed at the end of the run is burdensome. Why not simply measure the...
  10. R

    Energy Lost Due To Friction

    But how do you determine the instantaneous speed at the bottom of the incline so as to determine the kinetic energy? Isn't it easier to find the time difference between the theoretical and the real time of the descent? Ratch
  11. R

    Energy Lost Due To Friction

    Yes, but the length of the incline does not change once it is set up. The transit time does, depending on the friction. How can the change in time be used to compute the friction force or wasted energy? Ratch
  12. R

    Energy Lost Due To Friction

    While the above is true, it is the time of travel that relates to friction force and frictional energy lost. The time is also the easiest to measure. Ratch
  13. R

    Energy Lost Due To Friction

    Let me load you down with a few concepts and ideas. It stands to reason that the time it takes the trolley to roll down an incline will be dependent on the angle of the incline and the friction. Assuming no friction, can you calculate the time it will take a trolley to roll down an incline of...
  14. R

    Open / Short circuit time constants for pole approximation

    , I make no representations for the Open-circuit time constant method. I only calculated the Thevenin resistance. as requested by the OP and the book, of the B'--Vo terminals with rpi removed. I did this by using the combination Thevenin-Norton theorem method, which looks at the voltage and...
  15. R

    Open / Short circuit time constants for pole approximation

    At the start, I am calculating the open circuit voltage at B' and Vo. That is where the capacitor Cpi is connected. I should have said I removed rpi instead of Vpi. I need an open circuit to calculate the Thevenin impedance. Thevenin impedance is open circuit voltage divided by short circuit...
  16. R

    Open / Short circuit time constants for pole approximation

    Since you made a valiant try at determining the resistance that C_pi "sees", you deserve to see how it is done. Unlike the book, you can ask me to explain any facet of the solution you don't understand. You are going to have fun studying the solution. Ratch
  17. R

    Diodes Circuit analysis

    This problem has been hanging around for ten days now. If the OP hasn't been given the solution by the teacher by now, he should change schools. Sometimes, the full solution is a way of learning something. Others who read this thread might want to see the solution, too. Since the OP has not...
  18. R

    Diodes Circuit analysis

    Sorry I did not get to this problem sooner, but I was on vacation. It is assumed that the diodes will turn off if their voltage is less than 0.7 volts, or their current is less than 1 ma. Starting at -10 volts, it is easily observed that diode D1 will not conduct at this voltage, and D3 and D4...
  19. R

    Voltage and current relation difference between Ohm's law and Power

    First of all, Ohm's law is not V=I*R, and all its variations. Regardless of what predominates the electrical literature, a good physics book will tell you that Ohm's law is an electrical property of a material, specifically its electrical linearity. I can provide documentation for that...
  20. R

    Capacitors

    That depends on the voltage to which they are energized, and the value of their capacitance. Yes, you can de-energize them by shorting the two leads together, or connecting a low value resistor between the leads. A capacitor is an electrical energy storage device which stores energy in an...
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