What is the Fourier law of heat conduction?
Fourier's Law of Conduction states that the heat transferred through conduction is propotional to1.Area of cross section perpendicular to the direction of heat flow. (A)2.Temperature difference between the points causing the heat flow.3.Inversely propotional to he thickness of the material along which heat is flowing.MathematicallyQ(heat transferred) α Adt/dx[math]Q= -KA dt/dx[/math]where Q= Rate of heat transfer in WattA=Area of cross section perpendicular to the direction of heat flow in m^2dt=temperature difference causing heat flow in degree Celsiusdx=thickness of the material in metreK is the constant of proportionality and known as thermal conductivity of materialNote-[math] [/math]Negetive sign in the above expressions is due to the fact that that temperature of the body decreases as the thickness increases. So temperature gradient will be negative. So finally heat transferred becomes positive.Thank You
What is proof for Fourier's law of heat conduction?
Conduction: Conduction is the transfer of energy from the more energetic particles of substance to adjacent less energetic ones as a result of interactions between the particles.The mechanisms of heat conduction in different phases of a substanceConduction can take place in solids, liquids & gases. In gases & liquids, conduction is due to collisions & diffusion of molecules during random motion. In solids, conduction is due to combination of vibrations of molecules in lattice & energy transport by free electrons.Fourier’s Law of Thermal conduction :This general physical law is derived from empirical observations so no mathematical proof as expected.J. Fourier, who expressed it first in his heat transfer text in 1822.In experiment he have shown that, “ Rate of Heat Transfer through a plane layer is proportional to temperature gradient across the layer & heat transfer area.”In 1 D,In the limiting case of x →0, the equation above reduces to the differential formIn 3 D,(-)ve is given to satisfy 2nd law of Thermodynamics i.e. heat must flow downhill on temperature scale.Here, k is called Thermal Conductivity of Material that measures the ability of material to conduct heat. It is a property that depends on temperature but not on too extent. For all gases, k increase with temperature due to collision as result vibration increase.For more query:What is Fourier's Law of Heat Conduction?https://fenix.tecnico.ulisboa.pt...https://home.icts.res.in/~abhi/T...FOURIER'S LAW
Why does thermal conductivity of gases increase while liquids decrease with a rise in temperatute?
There are several mechanisms of heat conductivity present, as well as a handful of dissipative effects that counteract these various mechanisms.The most prominent way for a gas to conduct heat is through particle collisions. Particles in a place of higher temperature will have a higher mean velocity of their random motion. Thus, statistically speaking, upon collision with particles in a neighboring region, they will impart part of their momentum to these other particles, rather than the other way round, which leads to a propagation of the heat/energy through the gas.The higher the temperature, the faster and more erratic the motion of particles is, and thus also the number of collisions increases, which leads to an increase in the rate of heat transfer.Liquids are far more complicated. Depending on the theoretical model used, we can observe different temperature dependencies of the thermal conductivity - which agree with experiment for specific liquids in specific temperature ranges. It is difficult to nail down a single mechanism and it’s temperature dependence. What is important to note, though, is that in most liquids, when we assume (or experimentally enforce) constant density, the heat capacity increases with temperature, similarly to the gaseous state. It is just that thermal conductivity is inversely proportional to density (in our very simple model of particle collisions - the fewer particles, the fewer collisions and less heat transfer), and since density decreases with increasing temperature, the net effect is a decreasing thermal conductivity.There are also compounds that exhibit a non-monotonous temperature dependence of their thermal conductivity, due to different mechanisms fighting between each other, one dominating for a given temperature range, the other for another temperature range, both having vastly different temperature dependencies.
If we drop a metal ball and a wooden ball from same height at the same time, then which ball will reach the ground first?
The answer to this question will vary based on the situation. Let me elaborate it situation wiseExperiment conducted in total vacuum : In this case both the metal ball and the wooden ball will hit the ground at the same time!!!, irrespective of their shape, weights and sizes. The time required to hit the ground, depends on the acceleration of the object, which in this case if ‘g’ (gravity) acting same on both the objects.Experiment conducted in atmosphere: Here we have air which fills in the atmosphere. Air being a fluid, would enable two things - Buoyancy and air-resistance. In this case, the outcome of the experiment would depend on the following parametersShape of the balls - The ball with a more aerodynamic shape would touch the ground first. As it would have lesser air-resistance, thus the resultant acceleration acting on it would be more.Volume of the ball - The ball having lesser volume will hit the ground first. Since air is a fluid, buoyancy would act on it. Buoyancy is directly proportional to the volume ( ρ x V x g).Weight of the ball - The ball having higher weight will hit the ground first. This is because of the resistive force would have lesser impact on the net acceleration (g-a).In theory, as per Galileo, the answer is indeed straight forward! But life is not that straight forward.I hope this helps!
What happens when zinc reacts with hydrochloric acid?
Zn + HCl = H2 + ZnCl2It is a single displacement reaction where -Zinc is oxidised (it becomes positive) and water is neutralized. It is a reduction-oxidation reaction where one of the reactants loses oxygen and the other one gains.So, answering your question, we get hydrogen gas and a salt.Hydrogen gas, is identified by exposing it to a burning flame. It explodes (a bit,) with a pop sound. This is because Hydrogen is highly explosive.Hope it helped!