Question

Spring index is 10 and diameter of wire is 10 mm. Outer diameter of coil is __________

(a) 100 mm

(b) 90 mm

(c) 110 mm

(d) 120 mm

This question was posed to me by my school principal while I was bunking the class.

I want to ask this question from Construction of Helical Springs topic in division Curves used in Engineering Practice of Engineering Drawing

Answer 1

Correct answer is (c) 110 mm

For explanation I would say: Spring index = mean diameter of coil / diameter of wire, 10 = mean diameter /10 mm, mean diameter = 10 x 10 mm = 100 mm. Outer diameter = mean diameter + diameter of wire, Outer diameter = 100 mm+ 10 mm = 110 mm.