A thermometer uses:

1. water
2. mercury
3. air
4. none of the above

Which statement is correct:

1. Iron rims are cooled before they are placed on cart wheels.
2. A glass stopper gets tight on warming the neck of the bottle.
3. Telephone wires sag in winter, but becomes tight in summer.
4. A little space is left between two rails on a railway track.

In the process of convection, heat travels:

1. sideways
2. downwards
3. upwards
4. in all directions

The vacuum kept in between the walls of a thermos flask reduces the heat transfer by:

1. conduction only
2. convection only
3. radiation only
4. conduction and convection