The speed of a car and the time taken varies ___________ _______with each other.
Answers
Answer:
Speed & Time Taken vary Inversely with each Other bcoz As our Speed Increases, we can cover the Distance in short time. ☆ Distance Travelled & Time Taken. Distance Travelled & Time Taken vary Directly with each other bcoz As our Distance increases, the time to cover it also increases.
DefinitionEdit
Simple definitionEdit
Thermal conductivity can be defined in terms of the heat flow {\displaystyle q} across a temperature difference.
Consider a solid material placed between two environments of different temperatures. Let {\displaystyle T_{1}} be the temperature at {\displaystyle x=0} and {\displaystyle T_{2}} be the temperature at {\displaystyle x=L}, and suppose {\displaystyle T_{2}>T_{1}}. A possible realization of this scenario is a building on a cold winter day: the solid material in this case would be the building wall, separating the cold outdoor environment from the warm indoor environment.
According to the second law of thermodynamics, heat will flow from the hot environment to the cold one in an attempt to equalize the temperature difference. This is quantified in terms of a heat flux {\displaystyle q}, which gives the rate, per unit area, at which heat flows in a given direction (in this case the x-direction). In many materials, {\displaystyle q} is observed to be directly proportional to the temperature difference and inversely proportional to the separation:[1]
{\displaystyle q=-k\cdot {\frac {T_{2}-T_{1}}{L}}.}
The constant of proportionality {\displaystyle k} is the thermal conductivity; it is a physical property of the material. In the present scenario, since {\displaystyle T_{2}>T_{1}} heat flows in the minus x-direction and {\displaystyle q}is negative, which in turn means that {\displaystyle k>0}. In general, {\displaystyle k} is always defined to be positive. The same definition of {\displaystyle k} can also be extended to gases and liquids, provided other modes of energy transport, such as convection and radiation, are eliminated.
For simplicity, we have assumed here that the {\displaystyle k} does not vary significantly as temperature is varied from {\displaystyle T_{1}} to {\displaystyle T_{2}}. Cases in which the temperature variation of {\displaystyle k} is non-negligible must be addressed using the more general definition of {\displaystyle k}discussed below.