SOL1-2011 - ECH 152A, Fall 2010, Roland Faller Solution for...

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ECH 152A, Fall 2010, Roland Faller Solution for Homework 1, October 1, 2011 Problem 1 UNITS Electric current is the fundamental SI dimension with unit Ampere . For the following quantities combine fundamental SI units to obtain derived SI units Electric power, electric charge, resistance, and voltage. Solution Power P = U × I [ P ] = W = VA = J C C s = J s = kgm 2 s 3 Charge Q = I s [ Q ] = C = As Resistance R = U I [ R ] = Ω = V A = J CA = kgm 2 A 2 s 3 Voltage U = J Q [ U ] = V = J C = kgm 2 As 3 Problem 2 A mercury manometer at 25 C gives a reading of 71.38 cm at a point where the local acceleration of gravity is 9.82 ms - 2 . The atmospheric pressure is 100.78 kPa. What is the absolute pressure being measured? ( ρ Hg (25C) = 13 . 534 gcm - 3 . How does it change with the local acceleration of gravity? Solution The pressure measured in the manometer corresponds to p = ρgh = 13 . 534gcm - 3 9 . 82ms - 2 71 . 38cm = 13 . 534 × 9 . 82 × 71 . 38 × 10 3 kgm - 3 ms - 2
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SOL1-2011 - ECH 152A, Fall 2010, Roland Faller Solution for...

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