Question

A 12 ohm non insulated resistance wire is bent in the middle by 180° and both the halves are twisted with each other.What will be its new resistance?

Answer 1

Total resistance of the full length of the wire= 12 ohms

Resistance of the two pieces of equal length bent at the mid point and free ends brought together= 6 ohms. (because R is directly proportional to l and here l is halved so R for each will be half of the orignal value)

When you twist the wire the resistances of 6 ohms each are connected in parallel together, the effective resistance of the two wires connected in parallel:

1/R = 1/6 + 1/6 =1/3
Therefore effective resistance,Reff= 3 ohm.