(N/A) The circuit diagram is as shown in the image.
Join three resistors of different values in series. Connect them with a battery,an ammeter,a rheostat,and a plug key,as shown in the figure. Close the plug key. Note the ammeter reading. Change the position of the ammeter to anywhere in between the resistors. Note the ammeter reading each time. We observe that the value of the current in the ammeter is the same,independent of its position in the electric circuit. It means that in a series combination of resistors,the current is the same in every part of the circuit or the same current flows through each resistor.
Precautions:
$(i)$ The current should not be passed for a long time to avoid heating.
$(ii)$ All the connections should be tight.