The standard duration to boil an egg in an egg cooker is approximately 7 to 8 minutes for a hard-boiled egg and around 4 to 5 minutes for a soft-boiled egg. This timing is based on the assumption that the water in the egg cooker reaches a consistent boiling point and maintains it throughout the cooking process. The precise duration can vary slightly depending on the specific model of the egg cooker and the desired level of doneness for the egg.

The reason for these timeframes lies in the science of heat transfer and the physical properties of eggs. When an egg is placed in boiling water, heat is transferred from the water to the eggshell, which then conducts the heat to the yolk and white. The cooking time is sufficient to achieve the desired level of doneness without overcooking the egg, which can lead to a rubbery texture. According to the USDA Food Safety and Inspection Service, eggs should be cooked to an internal temperature of 160°F (71°C) to ensure they are safe to eat. The boiling process in an egg cooker typically reaches and maintains this temperature, resulting in a fully cooked egg.

For a hard-boiled egg, the longer cooking time allows the egg to absorb more heat, which leads to a firmer texture. On the other hand, a shorter cooking time for a soft-boiled egg ensures that the egg white is fully cooked while the yolk remains runny. It's important to note that the cooking time can be adjusted based on personal preference. For example, if you prefer your eggs to be a bit more runny, you can aim for the lower end of the cooking time range for soft-boiled eggs.

In conclusion, the recommended cooking times for eggs in an egg cooker are approximately 7 to 8 minutes for hard-boiled and 4 to 5 minutes for soft-boiled eggs. These times are based on the need to achieve a safe internal temperature while maintaining the desired texture of the egg.