How to connect a light bulb?

Question

Cables and wires

The task is as follows:
You need to insert a light bulb into the circuit near the switch so that when the switch is turned on, the heater works and the light turns on (to see that the heater is on). How to do it correctly so as not to pull additional wires?

Answer 1

As an option - a ferrite ring, through it - several turns of wire that goes to the load, to the secondary - several hundred turns of thin wire, a simple rectifier circuit and an LED.

Answer 2

Put indicator light

Answer 3

As already mentioned: current transformer + "bipolar" LED