Question

what type of expansion of mercury is used to calibrate a thermometer

Answer 1

positive expansion. As the volume of the mercury increase with increasing the temperature that is why its expansion type is positive.

Answer 2

To calibrate a thermometer,we can both use the negative and positive expansion of the mercury,it depends on the current status of the thermometer.

If the mercury level is in a upper place than the normal ,then we have to use the negative expansion to bring it down.

If the mercury level is in a lower place than the normal ,then we have to use the positive expansion to bring it up.