Chapter 32: Problem 15
Prove that the displacement current in a parallel-plate capacitor of capacitance \(C\) can be written as \(i_{d}=C(d V / d t)\), where \(V\) is the potential difference between the plates.
Short Answer
Expert verified
The displacement current is \( i_d = C \frac{dV}{dt} \).
Step by step solution
01
Understand the Parameters
In a parallel-plate capacitor, the electric potential difference between the plates is denoted by \( V \), and the capacitance of the capacitor is \( C \). The displacement current, \( i_d \), is related to the change in electric field (and thus the potential difference) over time.
02
Recall the Definition of Capacitance
Capacitance \( C \) is defined by the relationship \( Q = CV \), where \( Q \) is the charge on the capacitor and \( V \) is the potential difference.
03
Differentiate with Respect to Time
Differentiate both sides of the equation \( Q = CV \) with respect to time \( t \). This gives \( \frac{dQ}{dt} = C \frac{dV}{dt} \).
04
Relate to Displacement Current
The rate of change of charge with respect to time is defined as the current, \( i = \frac{dQ}{dt} \). Thus, using the earlier result, the displacement current is \( i_d = C \frac{dV}{dt} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Parallel-Plate Capacitor
A parallel-plate capacitor is a fundamental and straightforward electrical component. It consists of two large, flat plates that are parallel to each other. These plates are often separated by a small gap filled with an insulating material or vacuum.
- Each plate holds opposite charges, one positive and one negative.
- The charges build up an electric field between the plates.
- This field allows the capacitor to store energy effectively.
Electric Potential Difference
The electric potential difference, often termed as voltage, is crucial in the functioning of a capacitor. It represents the difference in electric potential between two points.
- In a capacitor, it is the voltage difference between the two plates.
- This potential difference causes the buildup of electric charge on the plates.
- Voltage is measured in volts (V) and denotes the energy per unit charge.
Capacitance
Capacitance is a measure of a capacitor's ability to store charge per unit potential difference. It is symbolized by the letter 'C' and is measured in Farads (F).
- A higher capacitance implies a capacitor can store more charge at the same voltage.
- The basic formula is given by \( Q = CV \), where \( Q \) is the charge and \( V \) is the voltage.
- Capacitance depends on factors like the area of the plates and the material between them.
Electric Field
The electric field is a core concept in understanding how capacitors work. It is a vector field around charged particles, and in a capacitor, it exists between the plates.
- The strength of the electric field is directly related to the voltage across the plates and the distance between them.
- A uniform electric field is established in a parallel-plate capacitor.
- This field is crucial as it relates to the force experienced by charges.