## Friday, May 2, 2008

### Past JEE Questions - Thermal Physics - Part 1

1984

1. At room temperature, the rms speed of the molecules of a certain diatomic gas is found to be 1930 m/s. The gas is

a. H2
b. F2
c. O2
d. Cl2

2. One mole of a monatomic ideal gas is mixed with one mole of a diatomic ideal gas. The molar heat capacity of the mixture at constant volume is ----------------.

3. 70 calories of heat are required to raise the temperature of 2 moles of an ideal gas at constant pressure from 30°C to 35°C. the amount of heat required (in calories) to raise the temperature of same gas through the same range (30°c to 35°C) at constant volume is

a. 30
b. 50
c. 70
d. 90

1986

Steam at 100°C is passed into 1.1 kg of water contained in a calorimeter of water equivalent 0.02 kg at 15°C, till the temperatur of the calorimeter and its contents rises to 80°C. The mass of the steam condensed in kilogram is

a. 0.130
b. 0.065
c. 0.260
d. 0.135

1987

State true or false

At a given temperature, the specific heat capacity of a gas at constant pressure is always greater than its specific heat capacity at constant volume.

1988

State true of false. Give very brief reasons

Two spheres of the same material have radii 1m and r4m and temperatures 4000 K and 2000 K respectively. The energy radiated per second by the first sphere is greater than by the second.

1989

300 g of water at 25°C is added to 100 g of ice at 0°C. The final temperature of the mixture is -------------°C.

Identify all correct alternatives
For an ideal gas
a. The change in internal energy in a constant pressure process from temperature T1 to T2 is equal to nCv(T2-T1), when Cv is the molar heat capacity at constant volume and n the number of moles of the gas.

b. The change in internal energy of the gas and the work done by the gas are equal in magnitude in an adibatic process.

c. The internal energy does not change in an isothermal process.

d. No heat is added or removed in an adiabatic process.