When a glass of water on a hot plate cracks but not when placed on top of an electric coil burner (induction stove), the reason lies in the different heating mechanisms of the two types of stovetops:
- Hot Plate (Electric Coil Burner): The electric coil burner heats up by conducting electricity through a resistive wire, which then generates heat. The heat is transferred from the electric coil to the metal coil housing and, finally, to the cookware placed on top of the coil. The electric coil burner heats both the cookware and the surrounding air.
Since the electric coil burner heats indirectly, the glass of water placed on it is exposed to the ambient air temperature in addition to the heat coming from the coil. Glass is relatively resistant to thermal shock, and the gradual increase in temperature allows it to expand more uniformly, reducing the risk of cracking. However, it's worth noting that placing a cold glass on a hot electric coil burner might still cause the glass to crack due to the temperature differential.
- Induction Stove: An induction stove uses electromagnetic induction to heat the cookware directly. The stove's magnetic field induces electrical currents in the base of the induction-compatible cookware. These electrical currents then generate heat directly within the cookware itself. The cookware essentially becomes the heating element.
When you place a glass of water on an induction stove, the glass itself does not get heated, and there's no direct transfer of heat from the stove to the glass. Instead, the water inside the glass might absorb some heat from the surrounding air due to conduction, but it won't reach a high enough temperature to cause the glass to crack. Additionally, glass is not magnetic, so it doesn't interact with the electromagnetic field generated by the induction stove.
In summary, the glass of water doesn't crack when placed on an induction stove because the stove doesn't directly heat the glass, and the induction process only affects magnetic materials like the induction-compatible cookware. On the other hand, a glass of water can crack on a hot plate because the glass is exposed to the surrounding hot air and the heat coming from the electric coil, which can lead to uneven expansion and potential cracking.