7 papers
Entropy production by simple electrical circuits
E. N. Miranda, S. Nikolskaia
The entropy production by simple electrical circuits (R, RC, RL) is analyzed. It comes out that the entropy production is minimal, in agreement with a well known theorem due to Pri…
What fuel for a rocket?
E. N. Miranda
Elementary concepts from general physics and thermodynamics have been used to analyze rocket propulsion. Making some reasonable assumptions, an expression for the exit velocity of…
Levitation in an "almost" electrostatic field
E. N. Miranda
It is well known that a charged particle cannot be in stable equilibrium in a purely electrostatic field. The situation is different in a magnetostatic field; consequently, magneti…
Minimum and terminal velocities in projectile motion
E. N. Miranda, S. Nikolskaya, R. Riba
The motion of a projectile with horizontal initial velocity V0, moving under the action of the gravitational field and a drag force is studied analytically. As it is well known, th…
How to get mechanical work from a capacitor and two batteries
E. N. Miranda
The work done by a parallel plate capacitor is evaluated when the plate separation is changed. Two cases are considered: 1) the capacitor has a constant charge; 2) the capacitor is…
On the maximum efficiency of realistic heat engines
E. N. Miranda
In 1975, Courzon and Ahlborn studied a Carnot engine with thermal losses and got an expression for its efficiency that described better the performance of actual heat machines than…