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Q102PE

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College Physics (Urone)
Found in: Page 864

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Short Answer

An RLC series circuit has a 1.00 kΩ resistor, a 150μH inductor, and a 25.0 nF capacitor. (a) Find the circuit's impedance at 500 Hz . (b) Find the circuit's impedance at 7.50 kHz . (c) If the voltage source has Vrms=408 V , what is Irms at each frequency? (d) What is the resonant frequency of the circuit? (e) What is Irms at resonance?

  1. The circuit's impedance at 500 Hz is 12.74 kΩ .
  2. The circuit's impedance at 5kHz is 1307.1Ω .
  3. The Irms at each frequency is 312 mA
  4. The resonant frequency of the circuit is 82187 Hz .
  5. The Irms at resonance is408 mA .
See the step by step solution

Step by Step Solution

Step 1: Definition of inductor and capacitor

A passive electrical component called an inductor stores energy in the form of a magnetic field. An inductor is a wire loop or coil in its most basic form. The coil's inductance is proportional to the number of turns it has.

A capacitor (also called a condenser) is a two-terminal passive electrical component that stores energy electrostatically in an electric field. Practical capacitors come in a variety of shapes and sizes, but they all have at least two electrical conductors (plates) separated by a dielectric (i.e., insulator).

Step 2: Given data

The resistance of the RLC circuit is R=1.00kΩ103Ω1kΩ=1.00×103Ω

The capacitance of the RLC circuit is C=25.0 nF10-9F1nF=2.50×10-8F

The inductance of the RLC circuit is L=150μ10-6H1μ=1.50×10-4H

Step 3: Write the formula for the capacitor

The reactance of an RLC circuit can be expressed as,

Z=R2+XL+XC2 ………………(1)

This means we'll need to figure out the capacitor and inductor's active resistances, which can be given as,

XC=12πfC ………………….(2)

XL=2πfL …………………..(3)

Step 4: Calculate the circuit's impedance(a)

We havef1=500 Hz , therefore substituting the given data in equations (2) and (3), we get,

role="math" localid="1654512552476" XC=12π×500Hz×2.50×10-8F =12.74×103Ω1kΩ103Ω =12.74 kΩXL=2π×500Hz×1.50×10-4H =0.314 Ω

Now, we use the above-obtained values of XC and XL in equation (3), and we get

Z=1.00×103Ω2+0.314Ω-12.74×103Ω2 =12.74×103Ω1kΩ103Ω =12.74 kΩ

Therefore, the circuit's impedance at 500 Hz is 12.74kΩ.

Step 5: Find the circuit's impedance(b)

We have f2=7.50 kHz103Hz1kHz=7.50×103Hz, therefore substituting the given data in equations (2) and (3), we get,

XC=12π×7.50×103Hz×2.50×10-8F =848.8 ΩXL=2π×7.50×103Hz×1.50×10-4H =7.07Ω

Now, we use the above-obtained values of XC and XL in equation (3), and we get

Z=1.00×103Ω2+7.07Ω-848.8Ω2 =1307.1Ω

Therefore, the circuit's impedance at 7.50 kHz is 1307.1Ω.

Step 6: Find   at each frequency(c)

According to Ohm's law, the root-mean-square intensity may be calculated using the reactance and the rms potential difference such that,

Irms=VrmsZ …………….(4)

For the frequency 500 Hz , the value of impedance is Z=12.74kΩ, therefore

Irms=408 V12.74kΩ =32.1mA

For the frequency 7.50 kHz , the value of impedance is Z=1307.1Ω, therefore

Irms=408V1307.1Ω =312.2 mA

Therefore, the Irmsat 500 Hz is 32.1 mA and at 7.50 kHz is 312.2 mA .

Step 7: Find the resonant frequency of the circuit(d)

The resonant frequency can be calculated using the expression,

f0=12πLC……………(5)

That indicates that in our case, the end outcome will be

f0=12π1.50×10-4H×2.50×10-8F =82187 Hz

Therefore, the resonant frequency of the circuit is 82187 Hz .

Step 8: Find Irms at resonance (e)

Remember that the resonant frequency occurs when the capacitor and inductor reactances are equal. If we look at the total reactance formula, this suggests that our resistance will be the same as the resistor. To put it another way, the rms current will be

Irms=408 V1000Ω =408 mA

Therefore, the Irms at resonance is 408 mA.

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