A metal rod having - -10- 10-6-C has a length of 250 cm at 40-C- The temperature at which it can be shortened by 1 mm -

At $40^{\circ} C$ , a brass rod has a length 50 cm and a diameter 3.0 mm. It is joined to a steel rod of the same length and diameter at the same temperature. What is the change in the length of the composite rod when it is heated to $240^{\circ} C$ ? The coefficients of linear expansion of brass and steel are $2.0 \times 10^{- 5}^{\circ} C^{- 1}$ and $1.2 \times 10^{- 5}^{\circ} C^{- 1}$ respectively.

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A metal rod having α=10×10−6/∘C has a length of 250 cm at 40∘C. The temperature at which it can be shortened by 1 mm :

The correct option is A 0∘CWe know, dl=lαdt where , dl= change in length and dt=change in temperatureSo, dt=dllαGiven, dl=1mm=10−3m l=2.5mPutting values we get, dt=40Since initial temperature = 40 degree centigrade, the temperature at which it can be shortened is 0 degree centigrade.

A metal rod having $α = 10 \times 10^{- 6} /^{\circ} C$ has a length of 250 cm at $40^{\circ} C$ . The temperature at which it can be shortened by 1 mm :