An electrical appliance may stop working after it's been unplugged for some time and then plugged back in again due to several reasons:
Power surge or voltage spike: When an appliance is plugged back in, it might experience a power surge or voltage spike in the electrical supply. This sudden increase in voltage can overload or damage the appliance's internal components, leading to a malfunction or failure.
Capacitor discharge: Some electrical appliances, especially those with motors or electronic components, have capacitors that store electrical charge. When the appliance is unplugged, these capacitors may still hold some residual charge. When you plug it back in, this sudden release of stored energy can cause stress on the internal circuitry or components.
Thermal effects: Electrical appliances generate heat during operation. When you unplug an appliance, it cools down, and when you plug it back in, the rapid change in temperature can cause thermal stress on the components, leading to failures over time.
Aging and wear: Over time, electrical components can degrade or wear out due to normal use. When an appliance is left unplugged for an extended period, the aging process might progress unnoticed. When you plug it back in, the worn-out components might fail due to the stress of powering up again.
Moisture or condensation: If an appliance was exposed to moisture or damp conditions while unplugged, it can lead to corrosion or short circuits when reconnected to power.
Software or firmware issues: In the case of smart appliances or devices with embedded systems, the software or firmware might experience glitches or errors when reconnected to power after being unplugged.
To minimize the risk of these issues, it's a good practice to unplug electrical appliances during lightning storms or if you expect an extended power outage. Additionally, using surge protectors or voltage stabilizers can help protect appliances from sudden voltage fluctuations. If an appliance stops working after being unplugged and plugged back in, it's best to have it inspected by a qualified technician to identify and address any underlying issues.