Chapter 1, Problem 1.35P

An electrical resistor is connected to a battery, asshown schematically. After a brief transient, the resistorassumes a nearly uniform, steady-state temperature of95°C, while the battery and lead wires remain at theambient temperature of 25°C. Neglect the electrical resistance of the lead wires.

(a) Consider the resistor as a system abut whicha control surface ¡s placed and Equation 1,12c is applied. Determine the corresponding values of ${\stackrel{\dot{}}{E}}_{in}\left(W\right),{\stackrel{\dot{}}{E}}_g\left(W\right),{\stackrel{\dot{}}{E}}_{out}\left(W\right),$ and ${\stackrel{\dot{}}{E}}_{st}\left(W\right)$ . If a controlsurface is placed about the entire system, what arethe values of ${\stackrel{\dot{}}{E}}_{in},{\stackrel{\dot{}}{E}}_g,{\stackrel{\dot{}}{E}}_{out},$ and ${\stackrel{\dot{}}{E}}_{st}$ ?
(b) If electrical energy is dissipated uniformly within theresistor, which ¡s a cylinder of diameter $D=60\text{mm}$ and length $L=250\text{mm}$ , what is the volumetric tatgeneration rate, $\stackrel{\dot{}}{q}\left({\text{W/m}}^3\right)$ ?
(e) Neglecting radiation from the resistor, what is theconvection coefficient?