On schematic diagrams, two vertical transformer windings with dashed parallel lines drawn between them typically indicate what type of core?

Introduction / Context:
Schematic symbols communicate not just connectivity but also construction details. For transformers and inductors, the presence or absence of core lines conveys whether the device is air-cored or uses a ferromagnetic core, which affects inductance, losses, and frequency range.

Given Data / Assumptions:

• Two vertical coils are drawn facing each other (transformer symbol).
• Dashed lines are shown between the windings.
• Standard drafting conventions used in many textbooks and datasheets.

Concept / Approach:
When a core is indicated between windings, it signifies magnetic material coupling the coils. In many basic schematic conventions, drawing parallel lines (often dashed or solid) between coils denotes a laminated iron (steel) core transformer, whereas no core lines implies air core. Specific CAD libraries may differentiate ferrite with variations, but the essential meaning is “magnetic core present,” commonly laminated iron in power-frequency contexts.

Step-by-Step Solution:
Identify the two parallel lines between windings as a core symbol.Associate this with laminated iron cores found in mains-frequency transformers.Therefore, dashed lines between the coils typically indicate an iron core transformer.

Verification / Alternative check:
Consult common schematic symbol references: air-core transformers are drawn without core lines; adding core lines indicates a ferromagnetic core, usually iron for power applications.

Why Other Options Are Wrong:
Air core would show no core lines at all.

“Nonmetallic core” is ambiguous; ferrite is nonmetallic but is usually identified more specifically and by context (high frequency).

Ferrite cores are often used at high frequency; many symbol sets still simply show core lines without distinguishing material.

Common Pitfalls:
Assuming the dashed style always encodes material type (iron vs ferrite). Unless the legend specifies otherwise, interpret lines between windings as “has ferromagnetic core,” which in power circuits typically means laminated iron.

Final Answer:
an iron core