What would happen if household lights were arranged in series?
There are two types of electrical connections: series connection and parallel connection. In a series connection, as the name suggests, all the devices are in a "series" and hence the circuit is only complete if all of them are controlled at once. This means that in a series connection, either all the devices would be switched on or switched off at the same time. There is no independent control of any device. In other words, a single switch will power on everything at home, which means the television, microwave, refrigerator, washing machine, all the lamps, heaters, air conditioners, etc. will be on or off at the same time.
The other disadvantage of a series connection is that there is a potential drop associated with each device. This means that depending on the resistance offered by each device, some devices may not get the rated power and hence will not be able to function appropriately and may get damaged early.
Thus, we prefer parallel connections at home, so that all the devices can be controlled separately and that each device gets the rated power.
Hope this helps.