Question

A wire of 9 resistance having 30 cm length is tripled on itself. What is its new resistance?

Answer 1

Case 1→↓

R = p l/a Here p = constant

9 ohm = p 30/a

a = 30/9 m²

now length becomes 1/3 rd and area tripled

Therefore a = 30/9 * 3 = 10 m² and l = 1/3 * 30 = 10 m

Now R = p l/a

R = 10/10 = 1 ohm