Unit03_4Ans

# Unit03_4Ans - 120 The Exponential Function f(t) = et/W...

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Unformatted text preview: 120 The Exponential Function f(t) = et/W Current i (mA) 100 W is called the time f(t) constant and is the time that it takes for e t W to reach 1 e, because f (W ) e W W e 1. 1.2 1 1 0.8 ) t 1 e ( f 0W 0 0.2 0 0 1 2 3 4 t 5 0.8 0.6 0.4 0 0 0 f 0 1 2 3 4 t 5 W (e f W  e 0 W ) W . 50 100 150 Time t (s) 200 250 What is the approximate value of the time constant W for this decay of electric current from a discharging capacitor in a simple RC circuit? A. 25 s. B. 35 s. C. 50 s. D. 100 s. 0.2 W e t W 20 0 1 e t W dt 40 0.4 1.2 ³ 60 0 0.6 e 1 | 0.37 | 3 8. f( t) df 1 t W 1  e , so dt W the slope of f (t ) at ) t df 1( . f t 0 is 0W W dt t 0 0 f 80 E. 250 s. Approximately, what was the discharging capacitor’s initial charge at time t 0? A. 1.2 C. B. 3.0 C. C. 6.0 C. D. 12 C. E. 18 C. Charge q q 6f 5 4 3 C 2 R 1 00 0 0 Charging50 100 Time150 t 200 250 When the charge on the capacitor drops to 1 2 of its initial value, the electric energy stored in the capacitor drops to what fraction of its initial value? B. 1 2 . A. 3 4. The graph shows the electric charge on a charging capacitor in a simple RC circuit. At time t 2W , how much charge is on the capacitor? B. 0.37qf . C. 0.63qf . A. 0.14qf . C. 12. D. 0.79qf . E. None of the above. E. 0.86qf . D. 1 4. ...
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## This note was uploaded on 12/27/2011 for the course PHYSICS 2208 at Cornell.

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Unit03_4Ans - 120 The Exponential Function f(t) = et/W...

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