A microwave heats up food quicker than a hob (stovetop), and the reason for this lies in the different mechanisms of heat transfer each appliance uses:
Microwave: Microwaves use electromagnetic waves at a specific frequency (usually around 2.45 gigahertz) to heat food. These microwaves penetrate the food and cause the water molecules inside it to vibrate rapidly. This vibration generates heat, which cooks the food from the inside out. Because the microwaves directly target the water molecules, which are present in most foods, the cooking process is relatively fast and efficient. Additionally, microwaves are capable of heating food evenly and quickly, as they don't rely on conductive or convective heat transfer.
Hob (Stovetop): A hob, or stovetop, uses either gas or electric coils to heat the bottom of cookware. When you place a pot or pan on the hob, heat is transferred through direct contact (conduction) from the hob's surface to the cookware, and then to the food. This process is slower compared to a microwave because it involves multiple steps of heat transfer. The cookware must first absorb the heat, and then the heat must be conducted through the food. Additionally, if the cookware has a lower thermal conductivity or there are air gaps between the cookware and the hob's surface, it can further slow down the heating process.
Overall, a microwave is faster at heating food because it utilizes electromagnetic waves to directly target and heat the water molecules inside the food, whereas a hob relies on conduction to transfer heat from the surface to the cookware and the food. However, the choice between using a microwave and a hob often depends on the type of food you're cooking, personal preferences, and the desired cooking results. Some dishes are better suited for stovetop cooking, while others are more efficiently heated using a microwave.