One of the most fundamental concepts encountered when studying "heat" and "temperature" in physics classes is expansion. While the long formulas written on the board sometimes make this topic feel like an abstract and distant concept, thermal expansion is actually an extremely ordinary natural phenomenon that we observe and even sometimes benefit from every day. In this article, we will examine examples from daily life showing how thermal elongation formulas move from laboratories to our kitchens, streets, and homes.
Let's start by recalling the basic rule: As temperature increases, the particles that make up substances vibrate faster and move further apart, which creates volumetric growth, i.e., expansion. If the elongation occurs predominantly in one direction (along the length), it is called linear thermal expansion and is calculated with the formula (ΔL = α·L₀·ΔT). For complex calculations, you can instantly see the values by using our Linear Thermal Expansion Calculator tool.
Now let's look at the reflections of this theory on the street.
Opening Stuck Jar Lids with Hot Water
It's a classic problem everyone has faced at least once in their life: The metal lid of a jam or pickle jar just won't open. The physics of thermal expansion lies directly behind your father or mother saying, "Let's turn it upside down and run it under hot water."
The jar itself is made of glass, and the lid is made of metal (usually tinned steel or aluminum). The expansion coefficient of glass is quite low compared to metals. When you hold the stuck lid under hot water, both the lid (metal) and the neck of the jar (glass) are subjected to the same temperature increase (ΔT).
Because metal has a much higher expansion coefficient (α) than glass, it expands rapidly when it receives heat. Because its diameter grows faster than the glass, the lid stops squeezing the mouth of the jar, loosens, and easily pops open. This situation is a wonderful practical application of the linear formula in an area and circular framework.
Sagging Power Lines in Summer
If you look carefully at the wires between electric poles while walking down the street, you will notice that the tension of the wires changes from season to season. In the summer months, the wires sag (loosen), drawing a much more pronounced downward curve. In the freezing cold of winter, they become almost as taut as a bowstring.
High voltage and transmission lines made from aluminum or copper alloys are kilometers long (a massive L₀ value). When they bake under the sun (ΔT increase), the formula (ΔL = α·L₀·ΔT) works ruthlessly. If the wires between the poles had been installed "fully taut" in the winter, during the winter cold (when ΔT is negative and ΔL works in the direction of contraction), the wires would want to shorten, pull the poles towards each other, and ultimately snap.
For this reason, engineers and technicians measure the ambient temperature when installing electrical wires and, applying the principles behind tools like the Linear Thermal Expansion Calculator, leave them loose (sagging) enough to prevent them from snapping in the winter.
A Daily Life Calculation Example (Power Line)
Let's say an aluminum wire 50 meters (50,000 mm) long is strung between two electric poles in front of your house. The expansion coefficient of aluminum is about 23 µm/(m·°C). Suppose the difference (ΔT) between the coldest night of winter (-5°C) and the hottest, sunniest day of summer (metal surface temperature 55°C) is 60°C.
How much will the length change (ΔL) in the wire be?
ΔL = 23 x 10⁻⁶ * 50,000 * 60 = 69 mm (That is, almost 7 centimeters!)
Even over a short distance of 50 meters, the wire elongates and shortens by 7 centimeters. Over longer distances and in hotter regions, this value can reach meters, making the sagging visible to the naked eye.
How Thermometers Work
Non-digital, old-fashioned glass wall thermometers are the most concrete example of volumetric thermal expansion in daily life. The 3-dimensional (volumetric) version of the linear expansion formula (ΔL = α·L₀·ΔT) applies to liquid thermometers.
There is mercury or colored alcohol in the bulb at the bottom of the glass tube. As the ambient temperature rises, the liquid heats up. Because the expansion coefficient of liquids is much higher than that of solids (glass), the heated liquid wants to expand. However, because the inside of the glass tube is very narrow (capillary tube), the expanding liquid is forced to rise (elongate) in one dimension upwards. By reading the lines on the tube, we read the amount of "elongation" of the liquid as degrees of temperature. In fact, the thermometer is not showing us the temperature, but the amount of expansion of the liquid.
Swelling or Popping of Parquet Floors at Home
Wooden and laminate floors also expand with changes in heat and humidity (because wood is heterogeneous, it expands with different coefficients in all directions). The craftsman laying the parquet in your house leaves 1-2 centimeter gaps at the bottom of the walls (so that they stay under the baseboards).
If the craftsman forgets to leave this expansion gap and lays the parquet flush against the wall, disaster begins when you turn on the boiler in winter in a house with underfloor heating. The heated parquets (L₀ gets bigger, ΔT is positive) want to elongate and expand. Because they rest against the wall, they cannot elongate, tension (stress) increases, and from the weakest point they find, usually the middle of the room, they swell up like a tent or make crackling sounds when you walk on them.
Common Mistakes and Misconceptions
The most common mistake made in daily life regarding thermal expansion is the misconception that the cavity (hole) of hollow objects (for example, a metal ring) will shrink when heated. However, according to the rules of physics, the hole inside a plate or ring expands outward as if the material were whole. That is, both the outer diameter and the inner diameter (hole) of a heated ring increase.
As can be seen, the phenomenon behind the Linear Thermal Expansion Calculator is not only the concern of engineers in the industry but a physical reality we are intertwined with when struggling with a jar lid or listening to the sound of parquets in the room. Understanding why the objects around us are produced in those dimensions and shapes provides us with a fun window showing how the world works.
