Why Don"t Birds get Shocked?

Why dont birds get sgocked when they just stand on a single wire..I mean the current is flowing in the wire just bcoz there is potential difference per unit length of the wire all along the wire..So as there is some potential difference when the bird keeps it's legs on 2 different places on the same wire current should flow thru its body and it shud get shock...But why it is not happened....
- Prudhvi Raj Borra (age 16)
Machilipatnam,Andhra Pradesh,India

Your statement that there would be a potential difference between the two legs of a bird perched on a high voltage transmission is correct.  But let's make a calculation and see how big it is.    Suppose the transmission line is 10 km long, the initial voltage is 10,000 Volts, and the ohmic loss along the line is 10% of the total, 1000 Volts.  Suppose the bird has its feet separated by  0.1m.  Then the voltage between its two feet is
1000 x 0.1/10,000 = 0.01 Volt.   That's not enough to shock the most sensitive bird foot.

LeeH  

(published on 01/29/2010)

If in that case why do we get shocked when we touch two adjacent High tension wires...Is it just because the currents in both the wires are flowing in opposite directions..If so even though the current is flowing in opposite directions the potential may be same between the two wires where we have catched the wires..But why does current flow through our body...Does both the wires possess same potential but opposite in sign...I am getting a little bit confused...
- Prudhvi Raj Borra (age 16)
Machilipatnam,Andhra Pradesh,India

Of the possibilities you mention, the closest is the last: the potentials in the 2 wires are opposite. In some real lines they may not be exactly opposite, but they are say 120° out-of-phase, so the voltage difference between them is still large.

Mike W.

(published on 01/31/2010)