Physic Labs

Problem 2

A resistor RR is connected to a source of emf E\mathcal{E} and internal resistance rr. Find the current and power dissipated in $R. Use an idealized laboratory-frame model: stated parameters remain constant during the process unless the motion itself makes a quantity vary. State a clear sign convention and use the defined symbols consistently. (a) Write the governing laws or constraints. (b) Derive the requested quantities symbolically and state their physical direction or meaning. (c) Check dimensions and examine a simple physical limit to validate the result. Finally, verify that every equation is dimensionally consistent and that the results satisfy the initial conditions. Since no numerical data are specified, the exact answers are expressions in the defined symbols.
PR is maximal at R=r,Pmax⁡=E24rP_R\text{ is maximal at }R=r,\quad P_{\max}=\tfrac{\mathcal E^2}{4r}
problems.proof.analysis

A simple limit or independent law provides a cross-check. If the result contradicts the expected physical trend, revisit the signs, approximations, or boundary conditions.