Question

A 4 ohm resistance wire is bent through 180° at its mid point and the two halves are twisted together. Then the resistance is(a) 1 Ω(b) 2 Ω(c) 5 Ω(d) 8 Ω

Answer 1

the answer is 85 ohm

Answer 2

Total resistance of the full length of the wire = 4ohm (Given)

Angle = 180° (Given)

Resistance of the two pieces of equal length bent at the mid point and free ends brought together= 2 ohms.

Resistance is directly proportional to length and inversely proportional to the c.s. area.

As R = p L/A and R is directly proportional to L

As, the wire is bent at mid  so, L = L/2

R = 2 ohm each

As, they are twisted together so, they are in parallel connection

1/r = 1/2 + 1/2

or, 1/r = 1/1

or, r = 1 ohm