Ferrites at High Frequency – Assertion–Reason Assertion (A): Ferrite cores are very useful at very high frequencies in inductors and transformers. Reason (R): Ferrites exhibit simultaneously high magnetic permeability and high electrical resistivity.

Introduction / Context:
Component designers prefer ferrites for radio-frequency and high-frequency power applications. The goal is to achieve large inductance and low loss as frequency increases. A material must provide strong magnetic response without allowing large eddy currents, which would otherwise waste energy and heat the core.

Given Data / Assumptions:

• Ferrites are ceramic, iron-oxide-based magnetic materials.
• They possess high relative permeability μr and very high bulk resistivity compared to metallic cores.
• Applications include SMPS transformers, chokes, RF inductors, and EMI suppression.

Concept / Approach:

Inductance scales with permeability (L ∝ μ), while eddy current loss scales roughly with f^2 and inversely with resistivity. Ferrites offer high μ to confine and enhance magnetic flux and, due to their ceramic nature, they have high resistivity that suppresses eddy currents even at high frequency. Hence, both statements are correct and the reason directly explains the assertion.

Step-by-Step Solution:

Verification / Alternative check:

Core loss curves provided by ferrite manufacturers show low loss up to MHz ranges, unlike laminated steels that suffer heavy eddy losses.

Why Other Options Are Wrong:

• R false: contradicts basic ferrite physics.
• R not an explanation: it clearly explains: high μ yields inductance; high ρ suppresses eddy currents.

Common Pitfalls:

Confusing ferrites with powdered iron; ignoring frequency-dependent permeability and loss tangent at very high frequencies.

Final Answer:

Both A and R are true and R is correct explanation of A