Heat generation is a process which involves the motion of particles. In simple words, heat can be explained by the working of molecules and the energy emitted by them creates heat or the emitted energy is converted into heat.
For example, when a person does exercise or any other activity, their body gets heated up and sweat is produced. Or during cooking when food gets warm or heated, it is simply the transfer of heat, through conduction or convection.
The reason behind the transfer of heat is scientific, it might seem easy and cliche to warm food but it has scientific reasons behind it. The invisible or microscopic particles get charged and energy is created which is transferred in the form of heat.
The process of transfer of heat can be direct or indirect, there are several materials as well in which heat can be transferred and in some, it cannot be transferred for example not all types of plastic cannot handle the heat.
The difference between conduction and convection is that in conduction heat is transferred directly whereas convection heat is transferred through the fluid. Both of them lead to the emission of heat but there are differences in method.
Comparison Table Between Conduction and Convection
|Parameters of Comparison||Conduction||Convection|
|Definition||Transfer of heat between two objects through direct contact.||Transfer of heat within the fluid.|
|State of matter||Solid||Liquid or gas|
|Transfer of electric current||Allows||Does not allow|
|Density of particles||High density||Low density|
|Rate of transfer of heat||Slow||Faster|
What is Conduction?
Conduction is the process of transfer of heat or current. Conduction is the transfer of energy in the form of heat and current from one atom to another through direct contact.
Conduction can happen in all three states of matter; solid, liquid and gas. The best transfer can occur in the solid-state because the atoms are tightly packed which enables the faster rate of transfer of, the density of molecules affects the rate of transfer of heat, on contrary liquid and gases are less efficient in the transfer of heat due to low density of molecules.
There are two types of conduction, those are conduction of heat and conduction of electricity.
Conduction of heat- when the temperature is increased in molecules a vibration is produced and this causes heat in molecules and then the transfer of heat is caused within the tightly packed molecules. For example, when a heating pad is applied on skin it causes heat in muscles too.
Conduction of electricity- it happens due to the movement of charged particles through any medium. This movement of charged particles causes a current which is carried by ions or charged electrons. For example, when current passes through wires, wires are made up of metal which is a good conductor of electricity.
There are several factors which affect the conduction, those factors are; the difference in temperature, length, cross-sectional area, and the material. Every material has different conductivity for example aluminium, bronze, copper, water, etc., will have different conductivity. Metals have the greatest conductivity.
The conduction can be calculated through formula in theory by several methods for example by Ohm’s law or by Fourier’s law. The rate of heat transfer is calculated by these formulae when the conductivity of the material is given. Conduction does not follow the law of reflection or refraction
What is Convection?
Convection is the process of transfer of heat through the bulk movement of molecules in any fluid. The initial transfer of heat between the object and fluid takes place due to conduction but afterwards, the bulk movement in particles of fluid creates convection.
The process of convection involves thermal expansion that is when a fluid is heated from below the surface the lower layer of liquid gets heated which gets thermally expanded the density of the molecule is more as compared to the liquid on the upper surface. Due to buoyancy the less dense particles the hotter liquid rises and colder liquid replaces it.
There are two types of convection, those are; natural convection and forced convection.
Natural convection- Type of convection in which difference in temperature causes a difference in densities, that is where buoyant force plays a major role. for example, oceanic winds.
Forced convection- a type of convection in which External forces induce convection for example fans, Water heaters, geyser, etc..
Factors that affect convection are; medium ( liquid or gas), temperature, a source which causes heat. One of the differences between conduction and convection is that convection does not support electric current.
Some examples of convection are; a land breeze ( occurs during the night ), or sea breeze (Occurs during the day), fans used for cooling up the room, heaters used for heating water, or steamers, etc..
Natural convection cannot be calculated easily but the forced Convection can be calculated theoretically through formula given by Newton’s law of cooling. The formula is:-
|P =dQ /dt =hA(T−T0)|
- P= dQ /dt- the rate at which heat is transferred
- h – convection heat-transfer coefficient
- A – exposed surface area
- T – the temperature of the immersed object
- T0 – the temperature of the fluid which is under convection
Main Differences Between Conduction and Convection
- Conduction takes place between objects through direct contact on the other hand convection takes place through the fluid.
- Conduction takes place better in solids on the contrary convection takes place better in liquid or gases.
- In conduction heat is transferred due to differences in temperature whereas in convection heat is transferred due to differences in density.
- The heat transfer in conduction is slow on the other hand the heat transfer in convection is fast.
- Conduction supports electric conduction as well but convection does not support electricity.
Conduction and convection both of them transfer energy in the form of heat.
Both of them can be natural or artificially produced depending upon their types.
Conduction and convection work in different states of matter ( solid, liquid and gas). The density of particles majorly affects conduction and convection.