Effects of Dielectrics in Capacitors

1. Introduction

A dielectric material is an insulating material which, when placed between the plates of a capacitor, changes its electrical properties. The presence of a dielectric significantly affects capacitance, electric field, and stored energy.

2. Effect on Capacitance

When a dielectric is inserted between capacitor plates, the capacitance increases.

C = K C₀

Where K is the dielectric constant and C₀ is the capacitance in vacuum.

3. Effect on Electric Field

The electric field inside the capacitor decreases due to polarization of dielectric molecules.

E = E₀ / K

4. Effect on Potential Difference

If the capacitor is isolated, the charge remains constant and potential difference decreases.

V = V₀ / K

If connected to a battery, the potential difference remains constant but charge increases.

5. Effect on Charge

When connected to a battery, the charge stored on plates increases.

Q = K Q₀

6. Effect on Energy Stored

The effect on energy depends on the condition:

• Isolated capacitor: Energy decreases
• Battery connected: Energy increases

7. Physical Explanation

Dielectric molecules get polarized and create an induced electric field which opposes the original field. This reduces the net electric field inside the capacitor.

8. Important Points

• Capacitance increases due to dielectric
• Electric field decreases
• Energy behavior depends on condition
• Dielectric constant K ≥ 1

Final Results (To Remember)

C = K C₀

E = E₀ / K

V = V₀ / K (isolated)

Dielectrics increase capacitance and reduce electric field inside capacitors.