A wire of cross sectional area 3mm2 is just stretched between two fixed points at a temperature of 20°C. Determine the tension when the temperature falls to 20°C. Coefficient of linear expansion α = 10–5 /°C and Y = 2 × 1011 N/m2.
(1) 120 KN
(2) 20 N
(3) 120 N
(4) 102 N
Correct Answer is: (3) 120 N
F = Y A α Δt
= 2 × 1011 × 3 × 10–6 × 10-5 × 20
F = 120 N.
