Electric furnace identification: An electric furnace in which heat is produced by an electric arc struck between each of three electrodes and the charge is called a/an ____ furnace.

Introduction / Context:
Electric furnaces are distinguished by how electrical energy becomes heat. In arc furnaces, an electric arc forms either between electrodes or between electrodes and the charge, delivering intense radiant and convective heat for high-temperature metallurgical processing (e.g., steelmaking). Recognizing the heating mechanism helps select equipment for specific materials and temperatures.

Given Data / Assumptions:

• Three electrodes suggest a three-phase AC arc furnace configuration.
• Heat is generated by an arc, not by resistive elements or induced currents in the charge.
• The charge directly receives energy from the arcs and hot plasma zone.

Concept / Approach:
Arc furnaces employ very high current and low voltage to strike arcs. The three-phase design provides thermal uniformity, high power density, and rapid melting, making it prevalent in electric steelmaking and foundry melting applications.

Step-by-Step Solution:
Identify mechanism: “arc struck between… electrodes and the charge”.Map to furnace type: this is characteristic of an electric arc furnace (EAF).Select the corresponding option: Arc furnace.

Verification / Alternative check:
Photographs and schematics of EAFs show three graphite electrodes penetrating the roof, arcs forming to the metal bath or scrap, confirming the description.

Why Other Options Are Wrong:
Resistance furnace: Heats via electric elements or the charge’s bulk resistance, no free-burning arc.Low-frequency induction furnace: Heats by eddy currents induced in the charge, not arcs.Dielectric furnace: Uses RF fields to heat non-conductors by dielectric losses.None of these: Incorrect, as “arc furnace” matches precisely.

Common Pitfalls:
Confusing induction heating (no arcs) with arc melting; the visible arc and three-electrode arrangement are key identifiers.

Final Answer:
Arc furnace