A capacitor is a two-terminal electronic component with the ability to store electrical energy in an electric field. It basically contains two conductive plates separated by an insulating material, known as a dielectric. Capacitors are extremely important components in many types of electronic devices and systems; therefore, understanding their principle of working and behavior is necessary for MDCAT students going to appear in physics examinations.
Definition and Working Principle
A capacitor is said to store energy when a voltage difference is applied across its plates. The bigger the voltage, the larger the electric field between the plates; this results in opposite charges accumulating on each plate. How much charge a capacitor can store depends on its capacitance, defined as the amount of charge stored per unit voltage:
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=
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C=
V
Q
Where:
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C is the capacitance (farads, F),
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Q is the charge stored on the capacitor (coulombs, C),
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V is the potential difference (volts, V).
Capacitance of a Parallel Plate Capacitor
The capacitance of a parallel plate capacitor is given by the formula:
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=
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∣∑
C=ϵ
d
A
Where:
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C is the capacitance (F),
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is the permittivity of the dielectric material between the plates (F/m),
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A is the area of one of the plates (m²),
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d is the distance between the plates (m).
The capacitance depends on the size of the plates, the separation between them, and the material used as the dielectric. The dielectric constant (
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ϵ
r
The dielectric constant of the material increases the capacitance, since it takes on more charge for a given voltage.
Types of Capacitors
Fixed Capacitors: These are capacitors with fixed values of capacitance, often chosen for particular uses in energy storage and signal filtering.
Variable Capacitors: These make it possible to mechanically or electronically alter capacitance; common in applications related to tuning circuits.
Electrolytic Capacitors: These are polarized capacitors with high capacitance values, often used in power supply filters.
Supercapacitors: These have very high values of capacitance and are used in energy storage applications in modern electronics.
Energy Stored in a Capacitor
The energy (
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E) stored in a charged capacitor is given by the formula:
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=
1
2
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2
E=
2
1.
CV
2
Where:
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E is the energy stored in the capacitor (joules, J),
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C is the capacitance (farads, F),
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V is the voltage between the plates (volts, V).
This energy can be released when the capacitor is discharged through a circuit.
Applications of Capacitors
Energy Storage: Capacitors store energy and release it when needed. They are applied in many areas, including power supply systems, cameras (flash capacitors), and backup systems.
Filtering: Capacitors smooth voltage fluctuations in power supplies by filtering out noise and reducing ripple in DC circuits.
Tuning Circuits: Capacitors are used in tuning circuits in radio receivers and transmitters for the selection of specific frequencies.
Signal Processing: Capacitors can be used in amplifiers and filters for the modification of signal frequency in communication systems.
MDCAT Quiz: Capacitor
The MDCAT Quiz on Capacitors often includes questions about the calculation of capacitance, energy storage, and the behavior of capacitors in different configurations. Students may be asked to find the capacitance of a capacitor with a given dielectric or to find how much energy is stored in a capacitor with a given voltage and capacitance value.
Free Flashcards for Capacitors
Free flashcards for capacitors provide an excellent way to review key concepts, such as:
The formula for capacitance (
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=
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C=
V
Q
)
Types of capacitors and their uses
Energy stored in capacitors (
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=
1
2
????️
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2
E=
2
1
CV
2
).
These flashcards will help MDCAT students solidify their knowledge and perform better on electrostatics and electronics-based questions.
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