(a) Explain what is meant by the statement that two bodies are in thermal equilibrium.

Q#1 (Past Exam Paper – June 2016 Paper 42 Q3)

(a) Explain what is meant by the statement that two bodies are in thermal equilibrium. [1]

(b) Suggest suitable types of thermometer, one in each case, to measure

(i) the temperature of the flame of a Bunsen burner, [1]

(ii) the change in temperature of a small crystal when it is exposed to a pulse of ultrasound energy. [1]

(c) Some water is heated so that its temperature changes from 26.5 °C to a final temperature of 38.0 °C.

State, to an appropriate number of decimal places,

(i) the change in temperature in kelvin, [1]

(ii) the final temperature in kelvin. [1]

 [Total: 5]

Solution:

(a) When two bodies are in thermal equilibrium there is no net transfer of energy between the bodies.

(b)

(i) thermocouple, platinum/metal resistance thermometer, pyrometer

(ii) thermistor, thermocouple

(c)

(i) change = 11.5 K

{The change in temperature in kelvin is the same as the same in temperature in degree Celsius.

Change = 38.0 – 26.5 = 11.5 K}

(ii) final temperature = 311.2 K

{Tempt in kelvin = tempt in degree Celsius + 273.15 = 38.0 + 273.15

Tempt in kelvin = 311.15 = 311.2 K

Since values of temperature are given to 1 d.p. in the question, the answer should also be given to 1 d.p.}