Question

Conduction is a transfer of heat energy that

		requires direct contact
		requires actual motion of substance
		it does not require matter
		all of the above

Answer 1

Heat is the form of energy that flows from body at high temperature to the body at low temperature. There are three modes of heat transfer: conduction, convection and radiation. Some media is required for transfer of by conduction and convection, but for radiation no media is required.

Conduction: The transfer of heat between two solid bodies is called as conduction. It depends on the difference in temperature of the hot and cold body. Example of conduction heat transfer is two bodies at different temperature kept in contact with each other. Another example is heating one end of the metal like copper; due to conduction heat transfer the other end of the metal also gets heated.

Convection: The transfer of heat between the solid surface and the liquid is called as convection heat transfer. Let us considering a vessel of water being heated, in this case heating of water due to transfer of heat from the vessel is convection heat transfer.

Radiation: When two bodies are at different temperatures and separated by distance, the heat transfer between them is called as radiation heat transfer. In case of the conduction and convection heat transfer there is a media to transfer the heat, but in case of the radiation heat transfer there is no media. The radiation heat transfer occurs due to the electromagnetic waves that exist in the atmosphere. One of the most important examples of radiation heat transfer is the heat of the sun coming on the earth.

Thus In conduction the transfer of heat energy requires direct contact, hence option-A is correct answer.