Capacitors and Capacitance Overview

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Questions and Answers

What is the primary purpose of a capacitor?

To increase the resistance in a circuit

To convert voltage into current

To store energy in an electrostatic field (correct)

To provide a direct current to the load

Which of the following equations describes capacitance?

C = Q - Vab

C = Q + Vab

C = Vab/Q

C = Q/Vab (correct)

What happens to capacitance if the area of the capacitor plates is increased?

Capacitance stays the same

Capacitance becomes zero

Capacitance decreases

Capacitance increases (correct)

What is the consequence of increasing the distance between the plates of a capacitor?

Capacitance decreases Signup and view all the answers

Which of the following correctly defines the unit of capacitance?

Coulombs per volt Signup and view all the answers

What characteristic of a dielectric affects the capacitance?

The nature of the insulating material Signup and view all the answers

In a parallel-plate capacitor, how is capacitance mathematically expressed?

C = ε0A/d Signup and view all the answers

If a capacitor holds a charge of 5 coulombs and has a voltage of 2 volts, what is its capacitance?

10 Farads Signup and view all the answers

What effect does a dielectric have on the capacitance of a capacitor?

It increases the capacitance. Signup and view all the answers

What is the relationship between voltage and the electric field in a capacitor?

Voltage is the product of electric field and distance between plates. Signup and view all the answers

If the charge stored in a capacitor is doubled, what happens to the energy stored in the capacitor?

It quadruples. Signup and view all the answers

When a dielectric material is introduced to a capacitor, what is its effect on the electric field between the plates?

It reduces the electric field. Signup and view all the answers

Given a defibrillator capacitor storing 73 J of energy and having a capacitance of 120 µF, what is the voltage across the capacitor?

3.0 kV Signup and view all the answers

Which of the following describes the dielectric constant (K) of a material?

It measures the reduction of electric field in a capacitor. Signup and view all the answers

For a parallel-plate capacitor with a capacitance of 7.0 µF and plate area of 1.5 m², how does the area relate to capacitance with dielectric present?

Increasing area increases capacitance. Signup and view all the answers

What happens to the potential difference in a capacitor when the charge is fixed and the dielectric material is introduced?

Potential difference decreases. Signup and view all the answers

Study Notes

Capacitors and Capacitance

A capacitor is an electronic component that stores energy in an electrostatic field.
A capacitor is essentially two conducting plates separated by an insulating material called a dielectric.
Capacitors are represented by symbols in circuit diagrams.
The more charge a capacitor can hold, the larger its capacity.
Charge is added to a capacitor by applying a potential voltage (pressure).

Types of Capacitors

Film dielectrics
"Wet" electrolytic capacitors
Ceramic capacitors
Polymer capacitors

Capacitance

Capacitance (C) is a measure of a capacitor's ability to store charge.
The formula for capacitance is C = Q/V_ab.
- Q = charge stored
- V_ab = potential difference between conductors
The unit of capacitance is the Farad (F).
Capacitance is related to the physical properties of the capacitor, such as the area of the plates and the distance between them.
In parallel-plate capacitors, capacitance increases with area and decreases with separation.

Parallel-plate Capacitor

A parallel-plate capacitor is composed of two parallel conducting plates separated by a small distance.
The capacitance of a parallel-plate capacitor in a vacuum is given by C = ε₀A/d.
- ε₀ = permittivity of free space
- A = area of each plate
- d = separation between plates
The capacitance of a parallel-plate capacitor filled with a dielectric is given by C= Κε₀A/d.
- Κ = dielectric constant

Energy Stored in a Capacitor

The energy stored in a capacitor is given by U = Q²/2C or U = 1/2 CV².
The stored energy increases with the amount of charge stored.
The stored energy is less for a fixed charge in a larger capacitor.

Dielectrics

Dielectrics are non-conducting materials placed between the plates of most capacitors.
A dielectric increases capacitance and energy density by a factor K.
The dielectric constant (K) of a material is the ratio of capacitance with the dielectric to capacitance without it (K = C/C₀).
Dielectrics reduce the electric field and voltage between the plates.

Dielectric Constant

The dielectric constant (K) measures how effectively a substance reduces an electric field in a capacitor.
A higher K value means a more effective reduction in the electric field and, thus, in voltage.

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Description

This quiz covers the fundamental concepts of capacitors, their types, and the principles of capacitance. Learn about how capacitors store energy, the formula related to capacitance, and the various types used in electronic circuits. Test your knowledge and understanding of these essential components in electronics.