Power dissipated in an RL circuit

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SUMMARY

The discussion centers on calculating the power dissipated in an RL circuit with a voltage of 216 V and a current of 6.10 A lagging by 36 degrees. The correct approach to find the power involves using the formula P = IV * cos(φ), where φ is the phase angle. The user initially miscalculated power using P = IR and RMS values incorrectly, leading to incorrect results. The final insight clarifies the necessity of incorporating the power factor derived from the phase angle into the power calculation.

PREREQUISITES
  • Understanding of RL circuits and their components
  • Knowledge of RMS voltage and current calculations
  • Familiarity with the concept of phase angle in AC circuits
  • Proficiency in using the power factor in power calculations
NEXT STEPS
  • Study the calculation of power in AC circuits using P = IV * cos(φ)
  • Learn about impedance in RL circuits and how to calculate it
  • Explore the significance of phase angles in AC circuit analysis
  • Investigate the differences between apparent power and real power in electrical systems
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Electrical engineering students, circuit designers, and anyone involved in analyzing AC circuits and power calculations.

pengumon
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Homework Statement



a) A circuit contains two elements, but it is not known if they are L, R or C. The current in this circuit when connected to a 2.16×102 V, 60.0 Hz source is 6.10 A and lags the voltage by 3.60×10^1 degrees. What are the two elements?

c) What is the power dissipated in this circuit?

Homework Equations



P=IV

The Attempt at a Solution



I determined that it was an LR circuit and calculated the impedance Z for part b) of the question but I'm stuck on the power. I did a simple P=IR to get an answer of 1.32E3 W but that was wrong, and I also tried dividing the I and V given by √2 to get rms values, then multiplying, which gave me 659 W but it's still wrong. Any insights or nudges in the right direction would be much appreciated!

Edit: I just realized my angle is 36 degrees, not 360 like I originally thought. That means I need to have a cos36 in there somewhere right? I'm still unsure as to whether I'm supposed to be using rms values or not though.
 
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pengumon said:

Homework Statement



a) A circuit contains two elements, but it is not known if they are L, R or C. The current in this circuit when connected to a 2.16×102 V, 60.0 Hz source is 6.10 A and lags the voltage by 3.60×10^1 degrees. What are the two elements?

c) What is the power dissipated in this circuit?

Homework Equations



P=IV

The Attempt at a Solution



I determined that it was an LR circuit and calculated the impedance Z for part b) of the question but I'm stuck on the power. I did a simple P=IR to get an answer of 1.32E3 W but that was wrong, and I also tried dividing the I and V given by √2 to get rms values, then multiplying, which gave me 659 W but it's still wrong. Any insights or nudges in the right direction would be much appreciated!

Edit: I just realized my angle is 36 degrees, not 360 like I originally thought. That means I need to have a cos36 in there somewhere right? I'm still unsure as to whether I'm supposed to be using rms values or not though.

You can assume that the voltage and current values given are RMS values unless otherwise indicated.

Note that the given current has a phase angle associated with it, which implies a power factor for the circuit. When they ask for power they want the real component of the complex power, which is the magnitude of the total power multiplied by the power factor.
 
I got it, thank you!
 

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