Capacitors | Jamb(UTME)

Types and Functions of Capacitors

1. A capacitor is a device that stores electrical energy in an electric field.
2. Capacitors are used in electronic circuits to regulate current, filter signals, and store energy.
3. Types of capacitors include ceramic, electrolytic, film, mica, and supercapacitors.
4. Ceramic capacitors are small and used in high-frequency applications.
5. Electrolytic capacitors store large amounts of energy and are used in power supply circuits.
6. Film capacitors are stable and reliable, ideal for precision applications.
7. Mica capacitors are durable and used in high-voltage applications.
8. Supercapacitors can store a large amount of energy and are used in energy storage systems.
9. Capacitors block direct current (DC) while allowing alternating current (AC) to pass.
10. They can smooth out voltage fluctuations in power supplies.
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Parallel Plate Capacitors

11. A parallel plate capacitor consists of two parallel conducting plates separated by a non-conductive material (dielectric).
12. The plates are charged with equal but opposite charges.
13. The dielectric material increases the capacitor’s ability to store charge.
14. Common dielectric materials include air, glass, mica, and plastic.
15. The electric field between the plates stores the energy.
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Capacitance of a Capacitor

16. Capacitance is the ability of a capacitor to store charge.
17. It is measured in farads (F).
18. A capacitor with a capacitance of 1 farad can store 1 coulomb of charge at 1 volt.
19. The formula for capacitance is $C = \frac{Q}{V}$, where $Q$ is charge and $V$ is voltage.
20. Larger capacitance means the capacitor can store more charge.
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Relationship Between Capacitance, Area, Separation, and Medium

21. The capacitance of a parallel plate capacitor depends on the area of the plates $(A)$, the separation between them $(d)$, and the dielectric constant $(\varepsilon_r)$ of the material.
22. The formula is $C = \varepsilon_0 \varepsilon_r \frac{A}{d}$, where $\varepsilon_0$ is the permittivity of free space.
23. Increasing the area of the plates increases capacitance because more charge can be stored.
24. Decreasing the separation between the plates increases capacitance because the electric field is stronger.
25. Using a material with a higher dielectric constant increases capacitance by reducing the electric field's strength.
26. Air has a dielectric constant close to 1, while materials like mica or ceramic have higher values.
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Capacitors in Series

27. When capacitors are connected in series, the total capacitance decreases.
28. The formula for capacitors in series is $\frac{1}{C_{total}} = \frac{1}{C_1} + \frac{1}{C_2} + \cdots$.
29. The total capacitance is less than the smallest individual capacitor in the series.
30. Series connections are used to achieve higher voltage ratings.
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Capacitors in Parallel

31. When capacitors are connected in parallel, the total capacitance increases.
32. The formula for capacitors in parallel is $C_{total} = C_1 + C_2 + \cdots$.
33. The total capacitance is the sum of all individual capacitances.
34. Parallel connections are used to achieve higher capacitance values.
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Energy Stored in a Capacitor

35. A capacitor stores energy in its electric field.
36. The energy stored is given by $E = \frac{1}{2} C V^2$, where $C$ is capacitance and $V$ is voltage.
37. The energy is measured in joules (J).
38. Larger capacitance or higher voltage results in more stored energy.
39. This stored energy can be released quickly, making capacitors useful in flash photography and power backup systems.
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Additional Key Points

40. Capacitors charge when connected to a voltage source and discharge when the circuit is completed.
41. The time taken to charge or discharge depends on the capacitance and the resistance in the circuit (RC time constant).
42. Polarized capacitors, like electrolytic ones, must be connected in the correct direction.
43. Non-polarized capacitors can be connected in any direction.
44. Capacitors in AC circuits create a phase shift between voltage and current.
45. A dielectric breakdown occurs if the voltage across the capacitor exceeds its rating, damaging it.
46. Capacitors can be used to tune radio frequencies by adjusting capacitance.
47. In power supplies, capacitors smooth out rectified AC into steady DC voltage.
48. Supercapacitors are increasingly used in renewable energy storage systems.
49. The dielectric loss of a capacitor affects its efficiency in storing and releasing energy.
50. Capacitors combined with resistors and inductors are used in filters and oscillators.

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