Induction electric furnaces — effect of induced currents and skin effect The electric furnace that develops heat by both induced currents and the skin effect is best described as which type?
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Aarc
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Bresistance
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Clow frequency induction
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Dhigh frequency induction
Answer
Correct Answer: high frequency induction
Explanation
Introduction / Context: Induction furnaces heat conductive charges via eddy (induced) currents generated by a time-varying magnetic field. At higher frequencies, current crowds near the surface (skin effect), intensifying surface heating and stirring (in coreless types).
Given Data / Assumptions:
- We compare heating mechanisms across furnace types.
- Skin depth decreases with frequency, heightening skin effect at high frequency.
Concept / Approach: Arc furnaces use arc radiation/resistance of the arc column; resistance furnaces heat via Joule heating in elements or the charge. Induction furnaces exploit induced currents; at high frequency, skin effect becomes pronounced, raising surface power density and enabling rapid melting/heating of metals.
Step-by-Step Solution:
Identify which furnace relies on induced currents: induction types.Recognize skin effect prominence: increases with frequency.Thus “high frequency induction” is the specific furnace where both induced currents and skin effect notably produce heat.Verification / Alternative check: Skin depth δ ∝ 1/√f; therefore, higher frequency reduces δ, intensifying surface current density and heating, matching high-frequency induction furnaces.
Why Other Options Are Wrong:
Arc — not induction-based.Resistance — Joule heating in elements/charge, not by induced eddies.Low frequency induction — reduced skin effect; heating is less concentrated at the surface.Common Pitfalls: Assuming all induction furnaces behave identically regardless of frequency; frequency selection is central to heating profile and penetration.
Final Answer: high frequency induction