# Quiz 3 (PHYS262, Summer 2001)

August 8, 2001

1
How many of the following statements are true?
1)
The change in the internal energy of a given system is equal to the sum of the heat given to it and the work done by it (i.e. ).
2)
In a constant-pressure (isobaric) process of a given system, the work done by the system is zero.
3)
In an isothermal (constant-temperature) process of an ideal gas, is satisfied. ( )
4)
The heat capacity of a given system is independent of the system size.
(a) Only one (b) Only two (c) Only three (d) All four (e) None

2
In Fig. 1 is shown a - (pressure-volume) diagram of a certain gas undergoing a cyclic process. In one cycle of the cyclic process, how much work is done by the gas? One unit of pressure and volume is respectively and in the graph.

(a) (b) (c) (d) (e)

3
A gas consists of hydrogen atoms (H) and hydrogen molecules (). At certain thermal equilibrium of the gas, the root-mean-square speed of a hydrogen atom is 400 m/s; what would be the root-mean-square speed of a hydrogen molecule in this gas?

(a) 283 m/s (b) 100 m/s (c) 200 m/s (d) 800 m/s (e) None of the above

4
How long does it take a 350 W coffeepot to boil off of water initially at . (The density of water is , the latent heat of vapourisation of water = and the specific heat of water is ).

(a) 6.1 min (b) 70 min (c) (d) 31 min (e) None of the above

5
How many of the following statements are true?
1)
The efficiency of a heat engine is only dependent on the highest temperature and the lowest temperature of a cycle.

2)
A refrigerator can extract heat from the lower-temperature system and convert it completely into mechanical work.

3)
A Carnot engine is an ideal engine with the perfect (100 %) efficiency.

4)
The entropy change in a reversible process is zero.

(a) Only one (b) Only two (c) Only three (d) All four (e) None