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  1. R

    Complete the circuit!

    Yes, reactance is dependent on the frequency. But the current amplitude and the phase together with the given voltage amplitude and phase determines the impedance. Frequency is not needed to solve this problem.
  2. R

    Complete the circuit!

    The problem asks for the resistance and reactance. The impedance gives you both those things directly. It does not ask you for the inductance because you need the frequency to calculate that from the reactance. No way around it, you need to become proficient dividing complex numbers to find...
  3. R

    Complete the circuit!

    Once you calculate the impedance, you can tell if it is inductive or capacitive by the sign of either the polar angle or the sign of the reactance. What does "search" mean in this context? Easy to figure out. Do you know how to calculate the impedance from the given voltage and current...
  4. R

    2 transistor circuit input output question.

    No, (8-VB)/10k is the emitter current. The base current is (8-VB)/(10k*(beta+1)). As mentioned before, the emitter resistor looks like 10k*(beta+1). You need the 20k resistor to be at least 10 times smaller than 10k*(beta+1) to stabilize the base voltage. Ratch
  5. R

    2 transistor circuit input output question.

    Current present in the 5k resistor splits into two paths. One path is through the 20k resistor, and the other is through transistor base and into the 10k emitter resistor. Looking in from the base side, the emitter resistor appears to be 10k * (1+beta). You want the current in the 20k...
  6. R

    2 transistor circuit input output question.

    Yes, the open circuit voltage would still be 8 volts, but now the Thevenin resistance would be comparable to 10k*beta. That would cause the bias to jump all over the place depending on what the base current is. It is recommended that the bottom base bias resistor be no more than 10% of the...
  7. R

    2 transistor circuit input output question.

    That is the correct way to do it. The reason is that the 20k bias resistor is so much smaller that the effective emitter resistance of beta*10k that the transistor base current is negligible compared to the base bias current. In other words, the bottom base bias resistor will control the bias...
  8. R

    tuned (tank) circuit, oscillator, Q

    True, but we have to start from somewhere. I am afraid I propagated that concept. You can make the L and C ratios anything you like as long as it doesn't get ridiculous, like the distributed capacitance of the inductor coils approaching the value of C. What I should have said is that the L...
  9. R

    tuned (tank) circuit, oscillator, Q

    To All: All I am saying is you can adjust the value of the oscillating circulating current of the tank circuit by using different L vs C ratios as long as the correct LC product is maintained. I can elaborate on this if anybody does not understand some aspect of what I said. In most cases...
  10. R

    tuned (tank) circuit, oscillator, Q

    One thing I would add. The energy, voltage, and current all oscillate. I will modify what I said about mismatching the L and C. As I said before, as long as the product of L and C are the same, the resonant frequency will be the same. If you increase L and lower C, the impedance of the tank...
  11. R

    tuned (tank) circuit, oscillator, Q

    I disagree. I explained very clearly what is going on. It is you who first denied that the current was circulating. Whether extra energy is supplied by the driver is irrelevant, the current is still circulating back and forth. Ratch
  12. R

    tuned (tank) circuit, oscillator, Q

    That in itself proves nothing. If something is taking energy from the tank circuit, whether a resistor or antenna, a damped sine wave will result. The tank circuit will still circulate the current with decreasing amplitude after each cycle unless replenished by the exciting voltage. Do you...
  13. R

    tuned (tank) circuit, oscillator, Q

    The top off is dependent on the energy loss due to resistance, so you cannot say that the top off is considerable unless you know the energy losses. If no losses, then no top off is needed. Are you telling me that the current in each branch is not alternating, and the phase of the current in...
  14. R

    tuned (tank) circuit, oscillator, Q

    You have been wrong about that for 40 years. A tank circuit circulates the current at the resonant frequency. In fact, once the circulation starts, the exciting voltage can be disconnected and it will circulate the current forever provided no resistance is present. Of course, it is impossible...
  15. R

    tuned (tank) circuit, oscillator, Q

    What is it I said that you do not understand? You have to understand what I am saying before you can reach a conclusion. Ratch
  16. R

    tuned (tank) circuit, oscillator, Q

    I think that is more complicated than it has to be. As long as the LC product is the same, the resonant frequency will be the same. The value of the circulating current at resonance is the exciting voltage across the tank circuit divided by either the inductive reactance or the capacitive...
  17. R

    tuned (tank) circuit, oscillator, Q

    There is nothing "magical" about them. They all follow the principles of physics. For a series resonant circuit, there is only one resonant frequency. For a parallel resonant circuit, some textbooks and folks define three frequencies. The first is where the capacitance and inductive...
  18. R

    Basic Physics Question

  19. R

    Basic Physics Question

    Yes, the energy which the charges expend flowing through the resistance is lost as heat. Less energy means a lower energy density of the charge or lower voltage where they exit the bulb. That is usually called a voltage drop. Correct, why should there be? There will be twice as much energy...
  20. R

    Basic Physics Question

    Partly. Energy = Voltage x Charge. So that means that if more charges lose some of their energy density, more energy is lost as heat. That is not pertinent to your understanding of this explanation. There is plenty of material that explains it if you are interested. Ratch
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