22P3Q06

6a)

From graph, $\displaystyle R=60\text{ }\Omega\text{ }$ when $\displaystyle \theta =20\text{ }{}^\circ \text{C}$

By PDP,

$\displaystyle \begin{aligned} \frac{r}{r+60}\times 1.50&=0.43 \\ 1.5r&=0.43r+25.8 \\ r&=24.1\text{ }\Omega\text{ } \end{aligned}$

COMMENT: This is a “show” question. So make sure you show all the substitution values explicity.

6b)

From graph, $\displaystyle R=40\text{ }\Omega \text{ }$ when $\displaystyle \theta =32\text{ }{}^\circ \text{C}$

$\displaystyle {{I}_{total}}=\frac{1.50}{40}+\frac{1.50}{24}=0.100\text{ A}$

xmPhysics