Re: what heat concept is more to do with electric kettles and why

You don't suppose it is a trick question, do you? I say that because all three modes of transfer of heat energy are important to the operation of a kettle! Notice that I have only said "three" instead of "four". "Insulation" is not a separate mode of heat-energy transfer but is rather related to heat conduction.

I am not going to directly answer the question for you, because that is what you are supposed to do, but I will guide your thinking and let you make your own conclusions.

Think about the heat energy in an electric kettle. Either the kettle is placed on an electrically heated surface of a stove or there are heating wires inside the kettle itself. Either way, the heat from the heating wires has to get to the kettle somehow, through the metal (or ceramic) of the kettle itself. What mode of heat-energy transfer would that be?

But there is also something inside the kettle that is supposed to be heated, whether it's stew or soup or.......! That something is in contact with the kettle itself, so the heat energy goes from the kettle's surface and into the "something" by way of the direct contact.

Now, the stuff inside the kettle is sometimes mostly liquid, in which case the stuff can move around if it gets heated unevenly and obtains density differences due to the different temperature of the various places in it. That mode of heat-energy transfer is....?

Both the kettle and the stuff inside are at temperatures at which objects give off electromagnetic energy ("light") at frequencies in the thermal infrared. That mode of heat-energy transfer is called ....?

There is also one other consideration which you didn't mention in your question! If the contents inside the kettle reach boiling temperature, a good portion of the heat energy is used to change the liquid to a vapor, which is called the "latent heat of vaporization".

So, which mode of heat transfer is the most important? Conduction, convection, or radiation? That's for you to decide and defend. I hope this answer has helped you in your thinking. There are also lots of previous answers in our archives that deal with heat transfer, conduction, convection, and radiation. You can find those answers by searching using our search engine.

John Link, MadSci Physicist