Molecular Physics | Thermodynamics Answers

A hot tungsten wire filament has a radius of 0.6cm a temperature of 300K and emissivity

0.74. Calculate the rate of energy emission by a 1.0m length of the wire. Ignore the radiation

received from the surrounding environment.

A sphere of radius 6.0cm at 1200oC is suspended in a vacuum in an enclosure at 500oC. Find

the rate of loss of heat, assuming that it is a black body

A 100cm3 measuring cylinder made from Pyrex glass is filled with glycerin to the

50cm3mark at 20oC. If the cylinder and content is heated to 40oC, to what mark will the

Glycerin rise? Take 𝛾𝑔𝑙𝑎𝑠𝑠 = 3 𝑥 10−6 𝑜𝐶 and 𝛾𝑎𝑙𝑐𝑜ℎ𝑜𝑙 = 500 𝑥 10−6 𝑜?

For an isotropic solid, show that the coefficients of expansion α, 𝛽 and 𝛾 are related as

(a) 𝛽 = 2𝛼

(b) 𝛾 = 3?

A container of glass has a volume 50cm3 . It is then filled to the brim with alcohol at 10oC.

The temperature is then raised to 40oC. Will the alcohol spill? If so, how much? Take

𝛾𝑔𝑙𝑎𝑠𝑠 = 9 𝑥 10−6 𝑜𝐶 and 𝛾𝑎𝑙𝑐𝑜ℎ𝑜𝑙 = 1.12 𝑥 10−4 𝑜𝐶

A room has 453cm3

of air at 20oC. If the temperature outside is 40oC, what volume of air

would remain in the room if the window is opened?

A glass block of 10 000cm3

volume is heated from 25oC to 40oC. The volume is found to

increase by 4cm3

Calculate the coefficient of cubical expansion of glass.

A brass sheet whose coefficient of superficial expansion is 3.1 x 10-4 oC-1

has its length 40cm

at 10oC. If the surface area at 110oC is 320.1cm2

find the width of the sheet.

An iron ring is to fit snugly on a cylindrical iron rod. At 20 oC, the diameter of the rod is

6.453cm and the inside diameter of the ring is 6.420cm. To what temperature must the ring

be brought if its hole is be large enough so it will slip over the rod? The coefficient of linear

expansivity of iron is 12 x 10-6 oC-1.

A pair of eyeglass frame is made of epoxy plastic. At room temperature of 23.4 oC, the

frames have circular lens 2.3cm in radius.

(a) Show that if the frames are heated to fit the lenses 2.32cm in radius, the temperature

required is given by

𝑇 = 𝑇𝑜 +

1

𝛼 (𝐿𝐿

𝑜 − 1)

With α the coefficient of linear expansivity of epoxy plastic.

(b) The coefficient of epoxy plastic is 1.3 x 10-4 oC-1

Calculate the temperature at which the 2.32cm lenses would be fitted into the frames.