Chapter 24: Problem 11
(1) To make a \(0.40-\mu\) F capacitor, what area must the plates have if they are to be separated by a 2.8 -mm air gap?
Short Answer
Expert verified
The plate area should be approximately 126.48 m².
Step by step solution
01
Understand the Capacitance Formula
The formula for the capacitance of a parallel plate capacitor is given by \( C = \frac{\varepsilon_0 \cdot A}{d} \), where \( C \) is the capacitance, \( \varepsilon_0 = 8.854 \times 10^{-12} \text{ F/m} \) (the permittivity of free space), \( A \) is the area of the plates, and \( d \) is the separation between the plates. We need to find \( A \).
02
Convert Units for Consistency
The given capacitance \( C = 0.40 \text{ }\mu\text{F} = 0.40 \times 10^{-6} \text{ F} \). The separation \( d = 2.8 \text{ mm} = 2.8 \times 10^{-3} \text{ m} \).
03
Rearrange the Formula to Solve for Area
Rearrange the formula to solve for \( A \): \[ A = \frac{C \cdot d}{\varepsilon_0} \]
04
Plug in the Values
Substitute the known values into the rearranged formula:\[ A = \frac{0.40 \times 10^{-6} \text{ F} \times 2.8 \times 10^{-3} \text{ m}}{8.854 \times 10^{-12} \text{ F/m}} \]
05
Calculate the Area
Perform the calculation: \[ A = \frac{1.12 \times 10^{-9}}{8.854 \times 10^{-12}} \approx 126.48 \text{ m}^2 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Capacitance
Capacitance is a measure of a capacitor's ability to store an electric charge. Simply put, it's like a "container" for electric charge, determining how much electric energy can be stored. Capacitance is denoted by the symbol \( C \) and is measured in Farads (F). The greater the capacitance, the more charge a capacitor can store at a given voltage.
Capacitance depends on several factors:
Capacitance depends on several factors:
- The surface area of the plates: Larger areas allow for more charge to be stored.
- The distance between the plates: Closer plates can store more charge.
- The material between the plates: Different materials affect how charge is stored.
Parallel Plate Capacitor
A parallel plate capacitor is a type of capacitor where two conductive plates are placed parallel to each other. This is a simple and common design used in various electronic devices. The space between the plates can be filled with air, a vacuum, or some insulating material, known as a dielectric, to enhance capacitance.
The ability of a parallel plate capacitor to store charge is calculated using the formula: \( C = \frac{\varepsilon_0 \cdot A}{d} \). Here,
The ability of a parallel plate capacitor to store charge is calculated using the formula: \( C = \frac{\varepsilon_0 \cdot A}{d} \). Here,
- \( \varepsilon_0 \) refers to the permittivity of free space, a constant value that represents how much electric flux is allowed through a vacuum.
- \( A \) is the area of one of the plates. Larger areas provide more space to store charge.
- \( d \) is the distance between the plates. Smaller distances increase the capacitance.
Permittivity of Free Space
Permittivity of free space, denoted by \( \varepsilon_0 \), is a fundamental physical constant describing how electric fields interact in a vacuum. It is used in calculating capacitance and appears in equations involving electric fields and forces. The constant has a value of approximately \( 8.854 \times 10^{-12} \text{ F/m} \).
The concept of permittivity is crucial in understanding how capacitors interact with electric fields:
The concept of permittivity is crucial in understanding how capacitors interact with electric fields:
- It determines how much electric field can "pass through" a certain space.
- Higher permittivity allows more electric field lines within a given space, enhancing the ability to store charge.
- In equations for capacitance, permittivity helps in determining the influence of the dielectric material between the plates.