The insulation between the two plates of a capacitor is called _______.

Question

Examoogle · Accepted Answer

dielectric

Explanation: A dielectric is an insulating material placed between the conductive plates of a capacitor. Its primary function is to increase the capacitance by reducing the electric field strength for a given amount of charge, preventing direct electrical conduction between the plates.

Working Principle: When a voltage is applied across the capacitor plates, the dielectric material undergoes polarization. Dipoles within the insulating material align themselves in the direction of the applied electric field, creating an opposing internal field. This partial cancellation of the net electric field reduces the potential difference $V$ across the plates, allowing the capacitor to store more charge $Q$ for a given potential, according to $C = \frac{Q}{V}$.

Key Formulas: $C = \frac{\epsilon A}{d}$ — Capacitance formula where $\epsilon$ is permittivity, $A$ is area, and $d$ is separation distance.; $E_{net} = E_{applied} - E_{polarized}$ — Net electric field reduction in the dielectric.

Key Points: Dielectrics are insulators that can be polarized by an electric field.; The constant of proportionality is called the relative permittivity or dielectric constant ($\kappa$ or $\epsilon_r$).; A perfect dielectric does not conduct current, but it can break down under an excessively high electric field (dielectric strength).

Advantages: Increases capacitance value significantly; Provides mechanical support between plates; Prevents arcing or short-circuiting between plates

Disadvantages: May undergo dielectric breakdown at high voltages; Can introduce leakage currents and power losses (dielectric loss)

Applications: Energy storage in electronic circuits; Filtering and smoothing in power supply units; Frequency tuning in oscillators

Additional Info: Common dielectric materials include mica, ceramic, paper, and plastic films like Mylar.. Option A (Conductor) would lead to a short circuit, Option B (Semi-conductor) allows partial conduction, and Option D (Superconductor) would create zero resistance, which is not suitable for plate insulation.

Answer: C is correct — The insulation between the two plates of a capacitor is known as a dielectric.

Exam Tip: Always remember that increasing the dielectric constant increases capacitance for the same plate geometry, but verify the voltage rating as it dictates the dielectric breakdown strength.

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