Thermal Phenomena

Understanding everyday thermal phenomena and heat-related effects

Topics

How does a refrigerator work?

A refrigerator works by using a refrigerant that evaporates inside (absorbing heat and cooling) and condenses outside (releasing heat). A compressor circulates the refrigerant, and the cycle continuously removes heat from inside the refrigerator, keeping it cold.

How does a thermometer work?

A thermometer works by using a substance that expands or contracts with temperature changes. Liquid thermometers use mercury or alcohol that expands in a narrow tube, with the height indicating temperature. Digital thermometers use temperature-sensitive electrical properties.

How does a thermos flask work?

A thermos flask (vacuum flask) works by minimizing heat transfer through three mechanisms: a vacuum between double walls prevents conduction and convection, reflective surfaces reduce radiation, and an insulated stopper prevents heat loss. This combination keeps hot liquids hot and cold liquids cold for extended periods.

How does an air conditioner work?

Air conditioners work by using a refrigeration cycle that transfers heat from inside to outside. A refrigerant circulates through coils, evaporating (absorbing heat) inside and condensing (releasing heat) outside. A compressor and expansion valve control the cycle, moving heat against the temperature gradient.

How does insulation work?

Insulation works by reducing heat transfer through conduction, convection, and radiation. Insulating materials trap air (a poor conductor), block convective currents, and reflect radiant heat. By creating barriers with low thermal conductivity, insulation slows heat flow, keeping warm spaces warm and cool spaces cool.

Why do we feel cold when wet?

We feel cold when wet because water evaporates from our skin, and evaporation requires energy (latent heat of vaporization). This energy comes from our body heat, cooling our skin and making us feel cold.

Why do we sweat when hot?

We sweat when hot because sweating cools the body through evaporation. When sweat evaporates from the skin, it absorbs heat energy (latent heat of vaporization), removing heat from the body. This cooling mechanism helps maintain body temperature within a narrow range despite external heat.

Why does hot air rise?

Hot air rises because it's less dense than cold air. When air is heated, molecules move faster and spread apart, decreasing density. Less dense air is buoyant and rises above denser cold air, creating convection currents that transfer heat upward.

Why does metal expand when heated?

Metal expands when heated because increased temperature makes atoms vibrate more, increasing the average distance between atoms. This thermal expansion occurs in all materials but is more noticeable in metals due to their rigid structure and common use in construction.

Why does wind feel cold?

Wind feels cold because it increases heat loss from your body through convection and evaporation. Moving air removes the warm air layer around your skin and increases evaporation of moisture, both of which cool your body faster than still air.