The base (soleplate) of an electric iron is brightly polished mainly for which physical reason?

Introduction / Context:
Electric irons used for pressing clothes have a metal base called the soleplate. If you observe carefully, this base is usually smooth and brightly polished or plated. While this may also make the appliance look attractive, there is a more important physical reason related to heat transfer. This question checks whether you can identify why a shiny surface is desirable in a heating appliance that aims to transfer its heat mainly by conduction to clothes.

Given Data / Assumptions:

• The base of an electric iron is brightly polished or shiny.
• The iron is used to press clothes by direct contact.
• Heat is generated by an internal heating element and must be delivered to the clothes efficiently.
• Possible reasons include smoothness, rust protection, reduced radiative loss and durability.

Concept / Approach:
Heat can be lost from a hot surface by conduction, convection and radiation. A polished, shiny metallic surface has a low emissivity, which means it emits and absorbs less thermal radiation compared to a dark or rough surface. Because an iron is designed to supply heat mainly by direct contact (conduction) with the cloth, it is desirable to minimise heat loss by radiation to the surrounding air. By making the base bright and shiny, radiative loss is reduced, so more of the energy goes into heating the clothes rather than being wasted as radiation to the environment.

Step-by-Step Solution:
Step 1: Recognise that the electric iron base is the main surface that becomes hot.Step 2: Recall that shiny, polished metallic surfaces have low emissivity and do not radiate heat as efficiently as dark, rough surfaces.Step 3: Understand that when ironing, we want most of the heat to be transferred directly to the clothes by conduction.Step 4: Reducing heat loss by radiation means more energy is conserved and the iron remains hot for effective ironing.Step 5: Conclude that the bright polish is mainly to reduce heat loss by radiation, not primarily for smoothness or rust prevention.

Verification / Alternative check:
Thermal physics teaches that dark, matte surfaces are good emitters and absorbers of radiation, while shiny, polished surfaces are poor emitters and absorbers. Many cooking pots, radiators and heaters use dark finishes when heat radiation is desirable. In contrast, when the goal is to keep heat in, shiny surfaces are preferred. This pattern matches the design of an iron soleplate, where conduction to the cloth is more important than radiative loss to the room.

Why Other Options Are Wrong:
Smoothness and low friction do help the iron glide more easily over fabric, but that is not the main physical reason emphasised in typical physics questions, which focus on heat transfer. Rust-proofing can be achieved through coatings, but the brightness itself is not the primary measure of rust resistance. Durability depends on material strength and design rather than just polish. Among the options, only reducing heat loss by radiation correctly connects the shiny base with its thermal function.

Common Pitfalls:
Students often focus on the mechanical convenience of a smooth surface and choose the option about frictionless motion. While that is a benefit, the question asks mainly about the physical reason connected to heat. To avoid confusion, remember the general rule: shiny surfaces are used when we want to decrease radiative heat exchange, and dull surfaces when we wish to increase it.

Final Answer:
The base of an electric iron is brightly polished mainly to reduce heat loss by radiation.