If the temperature field in a solid wall changes over time, the heat conduction process will be: Transient Equilibrium Steady-state Unstable

The correct answer is: Transient.<br /><br />When the temperature field in a solid wall changes over time, the heat conduction process is considered transient. In a transient heat conduction process, the temperature distribution within the solid wall varies with time, and the heat conduction rate is not constant. This is in contrast to a steady-state process, where the temperature distribution remains constant over time, and the heat conduction rate is constant.