"For low pressure differences the inclined manometer

shown in Fig. $2\mathrm{.}28$ is often used $($this device is so often

used to measure the "draft" of a furnace that its com$-$

mon name is a draft tube$).$

$($a$)$ If the scale is set to read zero length at $P_A=P_B$

and the manometer fluid is colored water, what

will the reading be at $P_A-P_B=0\mathrm{.}1lb\frac{f}{i}{n}^2?$

$($b$)$ What would the reading of an ordinary mano$-$

meter with vertical legs be for this pressure

FIGURE $2\mathrm{.}28$

Draft tube.

difference?