Mini Physics Now, what is the maximum fraction of the heat input that can be converted into work using cyclical processes? In 1824, a French engineer named Sadi Carnot described a theoretical engine, now called a Carnot engine, that is of great importance from both practical and theoretical viewpoints. He showed that a heat engine operating in an ideal, reversible cycle – …
Here are some of the physics videos that I’m sure you will be interested in. Note: If you like this post, you may also like Interesting TED talks. List The Elegant Universe Feynmann’s Lectures The Fabric Of The Cosmos Liquid Helium II, Superfluid _________________________ The Elegant Universe Watch here: Youtube playlist Feynmann’s Lectures Watch here: Project Tuva (Only Internet Explorer) …
Derivation of moment of inertia of an uniform solid sphere An uniform solid sphere has a radius R and mass M. calculate its moment of inertia about any axis through its centre. Note: If you are lost at any point, please visit the beginner’s lesson or comment below. First, we set up the problem. Slice up the solid sphere into infinitesimally thin …
The second law of thermodynamics is based on experimental observations. It places constraints on the direction of heat flow the attainable efficiencies of heat engines and heat pumps, beyond the first law which says only that energy has to be conserved. 2nd Law (Heat engines): The Kelvin-Planck statement It is impossible to construct a heat engine operating in a cycle, …
First law for an engine cycle says: Wout = Qh – Qc ,where Wout is work output by engine Qh is heat input from hot reservoir Qc is heat output to cold reservoir Thermal efficiency is defined to be the ratio of work output to the heat input from the hot reservoir per cycle, $$\begin{aligned} e \, &= \frac{W_{\text{out}}}{Q_{h}} \\ …
Heat pumps (refrigerators): The reverse of heat engines A heat pump is a device that uses mechanical energy to pump heat from a cold to a hot reservoir. If the heat engine is run in reverse, one gets a heat pump. In an analogous way, the heat pump must carry some working substance (usually a liquefiable gas) through a cyclic …
Isochoric Process In an isochoric process, the volume of the system is unchanged (ΔV = 0). Therefore, there is no work done on the system (i.e. W = 0). For such a process, the first law gives: $$\begin{aligned} \Delta E &= Q \\ &= n C_{v} \Delta T \\ &= \frac{C_{v} (P_{f} – P_{i})V}{R} \end{aligned}$$ This means that the heat …