Problem about rc and lr circuits

  • Thread starter kimduncanaimar
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In summary, the phase difference between voltage and current in both LR and RC circuits is not equal to 90 degrees due to the presence of resistance and stray capacitance in real inductors and capacitors. The total impedance of the circuit, which includes both resistance and reactance, determines the angle of the phase shift. As a result, the phase difference between voltage and current can vary from 90 degrees in these circuits.
  • #1
kimduncanaimar
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i hv done an experiment
but why the phase differencr between the voltage and current for both LR and RC circuits are not equal to 90?
moreover,how would a resisiance of a resistor affect the phase difference
between voltage and currentin capacitor?:cry:
at last,how would a resistor affect the phase difference between voltage and current in inductor?
 
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  • #2
The voltage and current in a capacitor or in an inductor are 90 degrees out of phase.
In an RC or LR circuit the voltage and current are out of phase by the angle of the total impedance Z = R + jX.
 
  • #3
SGT said:
The voltage and current in a capacitor or in an inductor are 90 degrees out of phase.
In an RC or LR circuit the voltage and current are out of phase by the angle of the total impedance Z = R + jX.

but from my result,it dosen't equal to degree of 90:cry:
 
  • #4
kimduncanaimar said:
but from my result,it dosen't equal to degree of 90:cry:

There is no pure inductance or capacitance.
A real inductor is made of a wound wire, so it has a resistance associated and this causes the phase shift to be different from 90 degrees.
There is also a stray capacitance between turns of the coil, that contributes to alter the phase.
In a capacitor the phenomenon is less important, but it has also a resistance and an inductance associated.
 

1. What are RC and LR circuits?

RC and LR circuits are electrical circuits that contain a resistor (R) and either a capacitor (C) or an inductor (L). These circuits are used to control the flow of current and voltage in a circuit.

2. What is the difference between RC and LR circuits?

The main difference between RC and LR circuits is the type of component they use to control the flow of current. RC circuits use capacitors, which store electrical charge, while LR circuits use inductors, which store energy in a magnetic field.

3. How do RC and LR circuits work?

In RC circuits, the capacitor charges and discharges, controlling the voltage in the circuit. In LR circuits, the inductor stores energy in a magnetic field, which creates resistance to the flow of current.

4. What are some applications of RC and LR circuits?

RC circuits are commonly used in timing circuits, such as in electronic watches and timers. LR circuits are used in power supplies and filters, as well as in electronic ignition systems for vehicles.

5. How do I calculate the time constant for an RC or LR circuit?

The time constant (τ) for an RC or LR circuit can be calculated by multiplying the resistance (R) by the capacitance (C) or inductance (L), respectively. τ = RC for RC circuits and τ = L/R for LR circuits.

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