Chapter 23: Problem 26
A series RCL circuit has a resonant frequency of \(690 \mathrm{kHz}\). If the value of the capacitance is \(2.0 \times 10^{-9} \mathrm{~F}\), what is the value of the inductance?
Short Answer
Expert verified
The inductance is approximately \(26.6 \text{ } \mu\text{H}\).
Step by step solution
01
Understand the Resonant Frequency Formula
The formula for the resonant frequency \( f \) of a series RCL circuit is given by: \( f = \frac{1}{2\pi \sqrt{LC}} \), where \( L \) is the inductance in Henrys and \( C \) is the capacitance in Farads. Our task is to find \( L \), the inductance.
02
Rearrange the Formula
We need to isolate \( L \) in the resonant frequency formula. Rearranging the equation to solve for \( L \), we get: \( L = \frac{1}{(2\pi f)^2 C} \).
03
Plug in the Given Values
Substitute the given values into the rearranged formula. The given resonant frequency \( f \) is \(690 \text{kHz} = 690 \times 10^3 \text{Hz}\) and the capacitance \( C \) is \(2.0 \times 10^{-9} \text{F}\). The equation becomes: \[ L = \frac{1}{(2\pi \times 690 \times 10^3)^2 \times 2.0 \times 10^{-9}} \].
04
Calculate the Inductance
Perform the calculations: 1. Calculate \( 2\pi \times 690 \times 10^3 \approx 4333796.25 \).2. Square the result: \( (4333796.25)^2 \approx 18781681852828.56 \).3. Multiply by the capacitance: \( 18781681852828.56 \times 2.0 \times 10^{-9} \approx 37563.3637 \).4. Take the reciprocal: \( \frac{1}{37563.3637} \approx 2.66 \times 10^{-5} \text{H} \).
05
Express the Result
The calculated inductance \( L \) is approximately \( 26.6 \text{ } \mu\text{H} \) (microhenries), since \( 1 \text{ } \text{H} = 10^6 \text{ } \mu\text{H} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Resonant Frequency
The concept of resonant frequency is essential in understanding how a series RLC circuit behaves. In these circuits, resonance occurs when the circuit's inductive and capacitive reactances cancel each other out. This happens at a specific frequency called the resonant frequency. At this point, the circuit is purely resistive, and the impedance is at its minimum possible value.
Resonant frequency is determined using the formula: \[ f = \frac{1}{2\pi \sqrt{LC}} \]where:
Knowing how to manipulate this formula allows engineers to design circuits that perform optimally at desired frequencies.
Resonant frequency is determined using the formula: \[ f = \frac{1}{2\pi \sqrt{LC}} \]where:
- \( f \) is the resonant frequency in Hertz (Hz)
- \( L \) is the inductance in Henrys (H)
- \( C \) is the capacitance in Farads (F)
Knowing how to manipulate this formula allows engineers to design circuits that perform optimally at desired frequencies.
Inductance Calculation
Calculating the inductance in a resonant circuit is a fundamental task when you know the resonant frequency and the capacitance. By rearranging the resonant frequency formula, you can solve for the inductance \( L \).
The formula becomes:\[ L = \frac{1}{(2\pi f)^2 C}\]This formula shows that the inductance required for a given resonant frequency is inversely proportional to the square of the frequency and directly proportional to the capacitance.
Steps for calculating inductance:
The formula becomes:\[ L = \frac{1}{(2\pi f)^2 C}\]This formula shows that the inductance required for a given resonant frequency is inversely proportional to the square of the frequency and directly proportional to the capacitance.
Steps for calculating inductance:
- Convert frequency from kilohertz to hertz if necessary (e.g., \( 690 \text{ kHz} = 690 \times 10^3 \text{ Hz} \)).
- Substitute the given frequency and capacitance values into the formula.
- Calculate \( 2\pi f \) and square it.
- Multiply the result by the capacitance.
- Take the reciprocal to find \( L \).
- Express the result in microhenries if needed, noting that \( 1 \text{ H} = 10^6 \mu\text{H} \).
Capacitance in Circuits
Capacitance is a measure of the ability of a system to store an electric charge. In the context of RLC circuits, capacitance plays a crucial role in determining the circuit's resonant frequency. A capacitor in a circuit can affect both the timing and frequency response characteristics.
Capacitors store energy in the electric field between their plates. The impact of capacitance in circuits involves several important aspects:
Capacitors store energy in the electric field between their plates. The impact of capacitance in circuits involves several important aspects:
- **Energy Storage:** Capacitors charge and discharge, allowing circuits to store energy temporarily, which can be essential for energy management solutions.
- **Filtering:** In AC circuits, capacitors block direct current (DC) while allowing alternating current (AC) to pass, making them useful for filtering applications.
- **Frequency Tuning:** Adjusting the capacitance in a circuit can change the resonant frequency, which is valuable in tuning radios or other frequency-dependent devices.