The reason clocks on microwaves (and some other household appliances) stop working during a power outage while stoves and refrigerators continue to function is related to the type of clock and power supply used in the appliances.
Clock type: Microwaves typically use digital clocks, which are more sensitive to power interruptions. These clocks rely on a constant supply of electricity to maintain the time display accurately. When there's a power outage, the digital clock loses its power source, causing it to reset and display the default time or no time at all.
Power supply: Stoves and refrigerators often have analog clocks or mechanical timers for basic functions like setting cooking time or defrosting duration. These analog clocks and mechanical timers do not require a continuous electrical supply to keep time or perform their basic functions. Instead, they use mechanical mechanisms or independent power sources, such as batteries, to keep track of time or remember their settings during brief power interruptions.
In modern microwaves, some high-end models may come with battery backup systems for their clocks, which allow the clock to retain the correct time during power outages. However, the majority of standard microwaves do not include this feature to keep costs down.
In summary, the difference in clock functionality during a power outage between microwaves and other appliances like stoves and refrigerators is due to the type of clock used and the presence or absence of battery backup systems.