The so-called 'zeroth law of thermodynamics' states that if the temperature of body $\mathrm{A}$ is equal to the temperature of body $\mathrm{B}$ and 

the temperature of body $\mathrm{B}$ is the same as body $\mathrm{C}$, then the temperature of body $\mathrm{C}$ equals the temperature of body $\mathrm{A}.$ 
Explain, in terms of energy flow, why the concept of temperature would be meaningless if this law was not obeyed.

. Figure shows a fixed mass of gas that undergoes a change from $\mathrm{A}$ to $\mathrm{B}$ and then to $\mathrm{C}.$

 During the change from$\mathrm{A}$ to$\mathrm{B}, 220 \mathrm{J}$of thermal energy (heat) is removed from the gas. Calculate the change in the internal energy of the gas.

Figure shows a fixed mass of gas that undergoes a change from $\mathrm{A}$ to $\mathrm{B}$ and then to $\mathrm{C}.$

During the change from $\mathrm{B}$ to C, the internal energy of the gas decreases by $300 \mathrm{J}$. Using the first law of thermodynamics explain how this change can occur. 

When a thermocouple has one junction in melting ice and the other junction in boiling water it produces an e.m.f. of $63\mathrm{\mu V}.$. 

What e.m.f. would be produced if the second junction was also placed in melting ice?

When a thermocouple has one junction in melting ice and the other junction in boiling water it produces an e.m.f. of $63\mathrm{\mu V}.$. 

When the second junction is placed in a cup of coffee, the e.m.f. produced is $49\mathrm{\mu V}$. Calculate the temperature of the coffee.

When a thermocouple has one junction in melting ice and the other junction in boiling water it produces an e.m.f. of $63\mathrm{\mu V}.$. 

The second junction is now placed in a beaker of melting lead at $327°\mathrm{C}$.

Calculate the e.m.f. that would be produced.

When a thermocouple has one junction in melting ice and the other junction in boiling water it produces an e.m.f. of $63\mathrm{\mu V}.$. 

The second junction is now placed in a beaker of melting lead at $327°\mathrm{C}$.

 State the assumption that you make.

The resistance of a thermistor at $0°\mathrm{C}$ is $2000 \mathrm{\Omega }$. At $100 °\mathrm{C}$ the resistance falls to $200 \text{Ω}$. When the thermistor is placed in water of constant temperature, its resistance is$620 \mathrm{\Omega }$.

Assuming that the resistance of the thermistor varies linearly with temperature, calculate the temperature of the water.