A barometer with brass scale, which is correct at 0^(0)C, reads 75.000 cm on a day when the air temperature is 20^(0)C . Calculate correct reading at 0^(@)C. (Coefficient of real expansion of mercury = 0.00018//^(@)C and coefficient of linear expansion of brass= 0.0000189//^(@) C. )

A barometer with brass scale, which is correct at 0^(0)C, reads 75.000

1.	A barometer with brass scale, which is correct at 0^(0)C, reads 75.000 cm on a day when the air temperature is 20^(0)C . Calculate correct reading at 0^(@)C. (Coefficient of real expansion of mercury = 0.00018//^(@)C and coefficient of linear expansion of brass= 0.0000189//^(@) C. )
Answer» Solution :We know `H_(0) = H (1 - (gamma - alpha) t )` . neglecting `gamma alpha ` term In this PROBLEM , H = 75.000 CM , t = `20^(@)` C `gamma = 0.00018 //^(@)C , "" alpha = 0.0000189//^(@) C ` `H_(0) = 75.000 [ 1 - (0.00018 - 0.0000189 ) 20]` `74.758` cm .