Q: Three disc A, B and C having radii 2 m, 4 m and 6 m respectively are coated with carbon black on their outer surfaces. The wavelengths corresponding to maximum intensity are 3000 nm, 4000 nm and 5000 nm respectively. The power radiated by them are QA , QB and QC respectively.
Q: 2 kg of ice at – 20 °C is mixed with 5 kg of water at 20 °C in an insulating vessel a negligible heat capacity. Calculate the final mass of water remaining in the container. It is given that the specific heats of water and ice are 1 kcal/kg/°C and 0.5 kcal/°C. While the latent heat of fusion of ice = 80 kcal/kg
(a) 7 kg
(b) 6 kg
(c) 4 kg
(d) 2 kg
Sol: Heat released by 5 kg of water when its temperature falls from 20 °C to 0°C is
Q1 = c m(ΔT)=103 × 5 × 20
= 0.2×105 cal.
This heat is used in raising the temp. of 2 kg of ice at – 20 °C to 0 °C and then melting it subsequently. Heat energy taken by 2 kg of ice at -20 °C to 0 °C and then melting it subsequently. Heat energy taken by 2 kg of ice at -20 °C in coming to 0 °C is
Q: A planet is at an average distance d from the sun and its average surface temperature is T. Assume that the planet receives energy only from the sun, and loss energy only through radiation from its surface. Neglect atmospheric effects. If T ∝ d -n , the value of n is
When a liquid in a glass vessel is heated, its apparent expansion is 10.30 × 10-4/°C. When the same liquid is heated in a metal vessel, its apparent expansion is 10.06×10-4/°C . If the coefficient of linear expansion of glass =9×10-6/°C, what is the coefficient of linear expansion of metal ?