A piece of wire of resistance 4 ohm is bent through 180° at its mid point and the two halves are twisted together, then find the resistance.
Total resistance of the full length of the wire= 4 ohms
Resistance of the two pieces of equal length bent at the mid point and free ends brought together= 2 ohms.
When you twiste the wire the resistances of 2 ohms each are connected in parallel together, the effective resistance of the two wire connected in parallel:
1/R = 1/2 + 1/2 =2/2= 1 , therefore effective resistance= 1 ohm.