19.7 Energy Stored in Capacitors
3 min read•june 18, 2024
Capacitors are essential components in electronics, serving various functions from filtering and energy storage to timing and tuning. They're versatile devices that can smooth out voltage fluctuations, provide short-term power, and create time delays in circuits.
Understanding how capacitors store energy is crucial. The energy stored depends on the and voltage squared. This principle is applied in medical defibrillators, where capacitors rapidly discharge a large amount of energy to restore normal heart rhythm during cardiac emergencies.
Applications and Energy Storage of Capacitors
Applications of capacitors in electronics
Top images from around the web for Applications of capacitors in electronics
Full Wave Rectifier and Bridge Rectifier - Electronics-Lab.com View original
Is this image relevant?
comparator - Timing circuit with op amps and capacitors - Electrical Engineering Stack Exchange View original
Is this image relevant?
Free Stock image of electronic filter | ScienceStockPhotos.com View original
Is this image relevant?
Full Wave Rectifier and Bridge Rectifier - Electronics-Lab.com View original
Is this image relevant?
comparator - Timing circuit with op amps and capacitors - Electrical Engineering Stack Exchange View original
Is this image relevant?
1 of 3
Top images from around the web for Applications of capacitors in electronics
Full Wave Rectifier and Bridge Rectifier - Electronics-Lab.com View original
Is this image relevant?
comparator - Timing circuit with op amps and capacitors - Electrical Engineering Stack Exchange View original
Is this image relevant?
Free Stock image of electronic filter | ScienceStockPhotos.com View original
Is this image relevant?
Full Wave Rectifier and Bridge Rectifier - Electronics-Lab.com View original
Is this image relevant?
comparator - Timing circuit with op amps and capacitors - Electrical Engineering Stack Exchange View original
Is this image relevant?
1 of 3
- Filtering and smoothing
- Remove ripples and noise from power supplies (voltage regulators)
- Smooth out voltage fluctuations in audio circuits (amplifiers)
- Energy storage
- Provide short-term power in electronic devices during power outages or switching (computers, clocks)
- Store energy in flash units for cameras (disposable cameras)
- Timing and oscillation
- Used in RC (resistor-) circuits to create time delays (timers, alarms)
- Determine the frequency of oscillation in resonant circuits (radio tuners)
- Coupling and decoupling
- Block DC signals while allowing AC signals to pass (coupling) (audio amplifiers)
- Prevent high-frequency noise from interfering with sensitive components (decoupling) (microprocessors)
- Tuning and filtering in radio and television circuits
- Adjust the frequency response of a circuit (bandpass filters)
- Filter out unwanted frequencies in radio and TV receivers (channel selectors)
Energy calculation for capacitors
- The energy stored in a is given by the equation:
- represents the energy stored in the capacitor, measured in joules (J)
- represents the capacitance, measured in farads (F)
- represents the voltage across the capacitor, measured in volts (V)
- The energy stored is directly proportional to the capacitance and the square of the voltage
- Doubling the capacitance doubles the energy stored (2F stores twice as much as 1F)
- Doubling the voltage quadruples the energy stored (20V stores four times as much as 10V)
- To calculate the energy stored:
- Determine the capacitance and voltage of the capacitor (10μF and 5V)
- Substitute these values into the equation ()
- Perform the calculation to find the energy stored in joules ()
- The energy stored in a capacitor is equivalent to the done to charge it
Capacitors in medical defibrillators
- A is a medical device that delivers a controlled electric shock to restore normal heart rhythm during cardiac arrest (ventricular fibrillation)
- The device uses one or more capacitors to store and quickly release a large amount of electrical energy
- The capacitors are charged to a high voltage (typically several thousand volts) (3000V)
- The stored energy is released in a short, intense burst when the defibrillator paddles are applied to the patient's chest (within 10ms)
- The high-voltage, short-duration electrical pulse depolarizes the heart muscle cells
- This allows the heart's natural pacemaker to re-establish a normal rhythm (sinus rhythm)
- Capacitors are ideal for this application because they can:
- Store a large amount of energy in a compact space (high energy density)
- Release the stored energy very quickly (in milliseconds) (fast discharge rate)
- Be recharged rapidly for multiple shocks if needed (within seconds)
- The energy delivered by the defibrillator is carefully controlled to provide the necessary shock without causing further damage to the heart (typically 200-360J)
Capacitor Physics and Electrostatics
- Parallel plate capacitors consist of two conductive plates separated by a material
- The capacitance is related to the plate area, separation distance, and the of the
- on the plates determines the strength between them
- The difference between the plates is proportional to the stored charge and inversely proportional to the capacitance
Key Terms to Review (26)
Capacitance: Capacitance is a measure of the amount of electric charge that can be stored in an electrical component or system. It is a fundamental concept in the study of electrostatics and the behavior of electric circuits. Capacitance is a crucial factor in understanding the storage and release of electrical energy, as well as the behavior of electrical components like capacitors.
Capacitor: A capacitor is an electrical component that stores energy in the form of an electric field, created by a pair of conductors separated by an insulating material. The ability to store charge is measured in farads (F).
Capacitor: A capacitor is a passive electronic component that stores electrical energy in an electric field. It consists of two conductors separated by an insulator, and it is used in various electronic circuits and devices to store and release electrical charge.
Charge Density: Charge density is a measure of the amount of electric charge per unit volume or unit area in a given material or region of space. It is a fundamental concept in electromagnetism and is crucial in understanding the behavior of conductors, insulators, and capacitors.
Conservation of Energy: Conservation of energy is a fundamental principle in physics that states the total energy of an isolated system remains constant, it is said to be conserved over time. Energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another.
Coulomb: Coulomb is the fundamental unit of electric charge, named after the French physicist Charles-Augustin de Coulomb. It is a measure of the amount of electric charge and is a crucial concept in understanding various topics in electricity and magnetism, such as static electricity, electric fields, electric potential, and the behavior of charged particles.
Coulomb force: Coulomb force, also known as the electrostatic force, is the force of attraction or repulsion between two charged particles. It follows an inverse-square law and is governed by Coulomb's law.
Coulomb's Law: Coulomb's law is a fundamental principle in electrostatics that describes the force of interaction between two stationary electric charges. It establishes a mathematical relationship between the magnitude of the electrostatic force, the charges involved, and the distance between them.
Defibrillator: A defibrillator is a medical device that delivers a dose of electric current (often called a counter-shock) to the heart to restore a normal heartbeat. It utilizes stored energy in capacitors to generate and deliver this high-voltage shock.
Dielectric: A dielectric is an insulating material that increases the storage capacity of a capacitor by reducing the electric field within it. Dielectrics are characterized by their ability to be polarized in the presence of an electric field.
Dielectric: A dielectric is an electrical insulator that can be polarized by an applied electric field. It is a material that does not conduct electric current under normal conditions, but it can support an electrostatic field by storing energy in the form of an electric field. Dielectrics play a crucial role in various topics related to electrostatics and capacitors.
Elastic potential energy: Elastic potential energy is the energy stored in an object when it is deformed elastically, such as when a spring is stretched or compressed. It can be calculated using the formula $U = \frac{1}{2} k x^2$, where $k$ is the spring constant and $x$ is the displacement from equilibrium.
Electric Field: The electric field is a vector field that describes the force experienced by a stationary, positive test charge at any given point in space. It represents the strength and direction of the electric force exerted on a charged particle by other charges in the vicinity, and is a fundamental concept in the study of electromagnetism and the behavior of charged particles.
Electrostatic Potential: Electrostatic potential is the potential energy per unit charge at a given point in an electrostatic field. It represents the work done per unit charge in moving a test charge from infinity to that point, and is a measure of the electric potential energy of a charged particle in an electric field.
Farad: The farad (symbol: F) is the unit of electrical capacitance in the International System of Units (SI). It measures the amount of electric charge that a capacitor can store for a given potential difference across its terminals.
Faraday cage: A Faraday cage is an enclosure made of conductive material that blocks external static and non-static electric fields by channeling electricity along and around the exterior. This effect is used to protect sensitive electronic equipment from electromagnetic interference.
Joule: A joule is the SI unit of work or energy, equivalent to one newton-meter. It measures the amount of work done when a force of one newton displaces an object by one meter in the direction of the force.
Joule: The joule (J) is the standard unit of energy in the International System of Units (SI). It represents the amount of work done or energy expended when a force of one newton acts through a distance of one meter. The joule is a fundamental unit that connects various topics in physics, from work and energy to thermodynamics and electricity.
Law of conservation of energy: The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. The total energy in an isolated system remains constant over time.
Parallel plate capacitor: A parallel plate capacitor consists of two conductive plates separated by a dielectric material. It stores electrical energy in the electric field created between the plates.
Parallel Plate Capacitor: A parallel plate capacitor is a type of capacitor consisting of two conductive plates separated by an insulating material called a dielectric. This arrangement creates an electric field between the plates, allowing the capacitor to store electrical energy.
Permittivity: Permittivity is a measure of the ability of a material to store electric energy in an electric field. It is a fundamental property that describes how an electric field affects, and is affected by, a dielectric medium. Permittivity is a crucial concept in understanding the behavior of electric fields, energy storage in capacitors, and the propagation of electromagnetic waves.
Potential Energy: Potential energy is the stored energy an object possesses due to its position or state, which can be converted into kinetic energy or other forms of energy. This term is central to understanding various physical phenomena and energy transformations in the context of introductory college physics.
Useful work: Useful work is the component of work that results in a desired outcome or effective energy transfer. It excludes any energy dissipated as waste, such as heat.
Volt: A volt is the unit of electric potential difference, which measures the amount of electric potential energy per unit charge between two points in an electric circuit. It helps us understand how much energy is available to move electric charges through a conductor, connecting it to concepts like power, energy storage, and circuit behavior.
Work: Work is a measure of the energy transferred by a force acting on an object as it is displaced. It is the product of the force applied and the distance moved in the direction of the force. Work is a fundamental concept in physics that is central to understanding energy, power, and the laws of motion.