There are two parallel transmission lines on electric poles. The potential
difference between these two lines is 240V throughout their lengths. If
you connect any conducting device across these two wires, it causes current
to flow between the wires. When the bird sits on a high voltage wire, there
is no potential difference between the legs of the bird because it stands on
a single wire. So no current passes through the bird. Hence, it doesn’t feel
any electric shock.

Measure the resistance of the bulb when it is in open circuit using a
multi meter. To measure the resistance of a bulb set the multi meter as
ohm meter and place the multi meter knob at 20K Ω. Now place the leads
of the multi meter on the terminals of the bulb. The meter will show one
of the following readings.

    0.00 or 1 or the actual resistance of the bulb.