A lead rod of length 60 cm joined at n en to an aluminium rod of length 120 cm. All measurement reer to 20o C. The coeicient o inear expansion of iron and aluminium are lead <img alt="=
A lead rod of length 60 cm joined at n en to an aluminium rod of length 120 cm. All measurement reer to 20o C. The coeicient o inear expansion of iron and aluminium are lead and then the average coefficient of the compoite system is .