25.1
Capacitores e Capacitância
Um dispositivo constituído por dois condutores elétricos que são separados por uma distância e utilizado para armazenar cargas elétricas é chamado de…
Considere uma luz solar, que carrega durante o dia e brilha à noite. Aqui, o capacitor armazena as cargas elétricas.
O capacitor mais simples consiste em duas placas condutoras paralelas separadas por vácuo.
Quando conectado a uma bateria, os elétrons do pólo negativo se acumulam na placa do capacitor conectada a ele, desenvolvendo uma carga negativa, enquanto a outra placa fica carregada positivamente.
Uma diferença de potencial que é igual ao produto do campo elétrico e à distância entre as placas é gerada através das placas até atingir a tensão da bateria. O campo elétrico é proporcional à carga e à área de superfície das placas paralelas.
Os capacitores carregados são descarregados quando conectados a uma carga e os elétrons fluem na direção inversa até que o potencial chegue a zero.
A quantidade de carga armazenada em um capacitor para criar uma determinada diferença de potencial é a capacitância, medida em unidades farad.
A capacitância para um capacitor de placa paralela é diretamente proporcional à área da placa e inversamente proporcional à distância entre as placas.
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Q1: How does a parallel plate capacitor store electrical charge?
A parallel plate capacitor consists of two conducting plates separated by a vacuum or insulating material. When connected to a battery, electrons accumulate on one plate, creating a negative charge, while the other plate becomes positively charged. A potential difference develops across the plates until it equals the battery voltage, allowing the capacitor to store electrical charge.
Q2: What is capacitance and how is it measured?
Capacitance is the quantity of charge a capacitor stores per unit of applied voltage. It is measured in farads (F), named after Michael Faraday, where one farad equals one coulomb per volt. Capacitance represents the ratio of maximum charge that can be stored to the applied voltage across the capacitor's plates.
Q3: How do plate area and distance affect capacitance?
Capacitance is directly proportional to the surface area of the parallel plates and inversely proportional to the distance between them. Increasing plate area increases the charge storage capacity, while decreasing the distance between plates strengthens the attraction of opposite charges, thereby increasing capacitance.
Q4: What happens when a charged capacitor is connected to a load?
When a charged capacitor connects to a load, it discharges as electrons flow in the reverse direction through the circuit. The potential difference across the plates decreases until it reaches zero, releasing the stored electrical energy to power the connected device.
Q5: How is the electric field related to charge in a parallel plate capacitor?
The electric field between parallel plates is directly proportional to both the charge stored and the surface charge density on the plates. Since surface charge density equals charge per unit area, the electric field magnitude increases with greater charge accumulation on the capacitor plates.
Q6: What role do dielectrics play in capacitor design?
A dielectric is an insulating material placed between capacitor plates to replace vacuum. Dielectrics enhance capacitance by allowing closer plate spacing and improving charge storage efficiency. Understanding dielectric properties like susceptibility, permittivity and dielectric constant helps optimize capacitor performance for specific applications.
Q7: What are practical applications of capacitors?
Capacitors have diverse applications including filtering static from radio reception and storing energy in medical devices like heart defibrillators. Solar lights use capacitors to store daytime electrical charge and release it at night, demonstrating how capacitors enable energy storage across many technological systems.