Question

Two solid objects, \(A\) and \(B\), are in contact. In which case will thermal energy transfer from \(A\) to \(B\) ? a) \(\mathrm{A}\) is at \(20^{\circ} \mathrm{C},\) and \(\mathrm{B}\) is at \(27^{\circ} \mathrm{C}\) b) \(\mathrm{A}\) is at \(15^{\circ} \mathrm{C},\) and \(\mathrm{B}\) is at \(15^{\circ} \mathrm{C}\) c) \(\mathrm{A}\) is at \(0^{\circ} \mathrm{C},\) and \(\mathrm{B}\) is at \(-10^{\circ} \mathrm{C} .\)

Short answer

a) A at 20°C and B at 27°C b) A at 15°C and B at 15°C c) A at 0°C and B at -10°C Answer: c) A at 0°C and B at -10°C

Step-by-step solution

Compare the temperatures in each case

In each case, compare the temperatures of object A to object B to determine which one has a higher temperature.

Case a: \(\mathrm{A}(20^{\circ} \mathrm{C})\) and \(\mathrm{B}(27^{\circ} \mathrm{C})\)

In this case, the temperature of B is higher than the temperature of A (\(27^{\circ} \mathrm{C} > 20^{\circ} \mathrm{C}\)). Therefore, thermal energy would transfer from B to A.

Case b: \(\mathrm{A}(15^{\circ} \mathrm{C})\) and \(\mathrm{B}(15^{\circ} \mathrm{C})\)

In this case, both objects have the same temperature (\(15^{\circ} \mathrm{C} = 15^{\circ} \mathrm{C}\)). Therefore, there would not be any thermal energy transfer between the two objects.

Case c: \(\mathrm{A}(0^{\circ} \mathrm{C})\) and \(\mathrm{B}(-10^{\circ} \mathrm{C})\)

In this case, the temperature of A is higher than the temperature of B (\(0^{\circ} \mathrm{C} > -10^{\circ} \mathrm{C}\)). Therefore, thermal energy would transfer from A to B.

Identify the correct case

Of these cases, it's clear that in Case c, thermal energy will transfer from A to B (A is at \(0^{\circ} \mathrm{C}\), and B is at \(-10^{\circ} \mathrm{C}\)). Therefore, the correct answer is option c.