Unformatted text preview: ECH 152A, Fall 2011, Roland Faller
Homework 1, October 1, 2012
Due: October 8, Beginning of Lecture
1. (4 points) UNITS
Electric current is the fundamental SI dimension with unit Ampere.
For the following quantities combine fundamental SI units to obtain derived SI
Electric power, electric charge, resistance, and voltage.
2. (4 points) A mercury manometer at 25 C gives a reading of 72.78 cm
at a point where the local acceleration of gravity is 9.81 ms2 . The atmospheric pressure is 100.78 kPa. What is the absolute pressure being measured?
ρHg (25 C) = 13.534gcm3 . How does it change with the local acceleration of
3. (4 points) The rst measurements of the properties of highpressure gases
(e.g. carbon dioxide) were made by Amagat in France in the 1860s and 1870s.
He worked in a mine shaft using a mercury manometer in a glass instrument
for pressures up to 400 bar (approx 40 MPa). (He actually later improved his
design to go to 3200 bar using a hydraulic design.) Estimate the size of the
instrument needed (for 400 bar). If you assume the diameter of the mercury
column was 1 cm, what was the weight of the mercury in the instrument?
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