Final answer:
The application of thermal paste between a CPU and heatsink is done to improve heat transfer by filling in gaps that would otherwise trap air, which is a poor heat conductor.
Step-by-step explanation:
The purpose of applying thermal paste between the CPU (Central Processing Unit) and heatsink is to enhance the thermal conductivity between these two components. The thermal paste works by filling in the microscopic gaps and imperfections on the surfaces of the CPU and heatsink, which, if left unfilled, would trap air. Air is a poor conductor of heat, so by replacing this air with thermal paste, you increase heat transfer significantly, thereby keeping the CPU cooler and improving its efficiency and longevity. Thermal paste ensures that more of the heat generated by the CPU is conducted away by the heatsink, preventing overheating and potential damage.