*State the thermometric property that defines the temperature scale in a liquid-in-glass thermometer.
- Volume of a fixed mass of liquid.
*Describe how you would calibrate an unmarked mercury-in-glass thermometer.
- Place the bulb of the unmarked thermometer in pure melting ice at a pressure of 1 atmosphere.
- When the mercury level is steady, mark this position as 00C.
- Next, place the bulb of the unmarked thermometer in steam above boiling water at pressure of 1 atmosphere.
- When the mercury level is steady, mark this position as 1000C.
- Divide the interval between 00C and 1000C into 100 divisions.
- Each division represents 10C.
*Explain what it meant by responsiveness of the thermometer.
- A responsive thermometer reacts quickly to changes in temperature.
*Explain what is meant by sensitivity of the thermometer.
- A sensitive thermometer gives a more noticeable expansion (large increase in the length of the mercury thread) for small changes in temperature.
*State the set up of a thermocouple and describe how works.
- A thermocouple consists of two types of wires made of different metals.
- The ends of the wires are joined to form two junctions.
- When the two junctions are at different temperature (one hot and one cold), a small voltage (e.m.f) is produced.
- The greater the difference, the greater the voltage produced across the two junctions. That is, the voltage produced is proportional to the temperature difference.
- By knowing one reference temperature and measuring the voltage, the unknown temperature can be found.