why is there a limit in a number of devices connected in a circuit?

Answer 1

I'm assuming you mean the number of devices plugged into wall sockets for a single circuit. The reason is that all the sockets are in parallel to the main line. As you add more devices in parallel the line resistance decreases and the line current by way ohm's law increases. There's a safety limit to the amount of current allowed per line. Exceed the limit and the breakers trip or the fuses blow.

Answer 2

Limiting the number of devices that can be connected to a circuit in a house is a simple if imprecise safety measure.

The circuit in the house will have a maximum capacity that will depend on the gauge of the wire and whether a ring main has been used. Above that capacity there is a risk that the heat generated in the wire could cause a fire.

It is obviously unrealistic to check the load on every device before using it, so a simple limit is put on the circuit.

Answer 3

There is no limit to the number of devices that can be connected, only a limit to the total current drawn from the circuit. So if you have a circuit with a 15-amp breaker in it, you can connect 15,000 devices if each device only drew 1 milliamp of current.

Answer 4

So you don't blow the fuse which can only handle so much electricity.