Final answer:
Energy is transferred through the copper wall of the tank by conduction and within the water by convection. Doubling the voltage on an immersion heater will decrease the heating time but could be hazardous.
Step-by-step explanation:
The process by which energy is transferred through the copper wall of the tank in an electric immersion heater is known as conduction. Conduction occurs when heat energy is transferred through a material without the material itself moving. The heat generated by the immersion heater is first conducted through the metal wall of the heater and then the heat transfer to other parts of the water occurs mostly by convection. During convection, the hotter water expands, its density decreases, and it rises to transfer heat to other regions of the water, while the colder water sinks toward the bottom, creating a circulation pattern. This process continues, creating a uniform temperature within the water. If the voltage applied to an immersion heater is doubled, the time required to heat the water will decrease because the power, which is proportional to the square of the voltage (P = V²/R), will increase. However, doubling the voltage could also be dangerous and may potentially damage the electrical circuit or the appliance itself.