Capacitance JEE NOTES PHYSICS

What is a Capacitor?

• A capacitor is a device that stores electrical energy in an electric field.

• It does not generate energy; it just stores and releases it when needed.

• Think of it like a tiny rechargeable battery in a circuit.

2. Structure of a Capacitor

• Two Conductors (Plates): Usually metal plates.

• Dielectric Material: An insulator (like air, paper, mica) placed between the plates.

• When connected to a battery, opposite charges accumulate on the two plates.

3. What is Capacitance?

• Capacitance is the ability of a capacitor to store charge.

• Higher capacitance means it can store more charge at the same voltage.

• It depends on:

  1. Area of the plates – larger area = more charge storage.

  2. Distance between plates – closer plates = stronger electric field, more storage.

  3. Dielectric material – better insulating material = higher storage.

4. Types of Capacitors

1. Fixed Capacitors: Capacitance is constant. Examples:

   • Ceramic capacitor

   • Mica capacitor

   • Electrolytic capacitor

2. Variable Capacitors: Capacitance can be adjusted.

   • Used in radio tuning circuits.

5. Combination of Capacitors

1. Series Connection:

   • Capacitors connected end to end.

   • Useful when you want smaller total capacitance.

2. Parallel Connection:

   • Capacitors connected side by side.

   • Useful when you want larger total capacitance.

6. Energy Stored in a Capacitor

• A capacitor stores energy in the electric field between its plates.

• When connected in a circuit, it can release this energy quickly, which is useful in:

  • Flash of a camera

  • Power backup systems

  • Smoothing voltage in electronics

7. Key Notes for Exams

• Capacitor = device that stores charge and energy.

• Capacitance depends on plate area, distance, and dielectric.

• Dielectric increases capacitance.

• Series vs Parallel connections affect total capacitance differently.

• Applications: energy storage, filtering, timing circuits, cameras, radios.