physics uuunu. Name An uncharged capacitor and a resistor are connected in serie
ID: 1327868 • Letter: P
Question
physics uuunu. Name An uncharged capacitor and a resistor are connected in series to a source of emf. If the source is 9.00 V, C = 20.0 F, and R-100 , find 1. a) The time constant of the circuit b) The maximum charge on the capacitor c) The charge on the capacitor after two time constants Create a plot of charge vs time for the capacitor in Problem 1 above. Do it for a range of time values that vary from 0 to 6 time constants. Submit the graph with this pre-lab. 2. The heating element of a coffeemaker operates at 120 V and carries a current of 2.00 A. Assuming the water absorbs all the energy converted by the resistor, calculate how long it takes to heat 0.500 kg of water from room temperature (23.0 C) to the boiling point. 3. Time =Explanation / Answer
given voltage v = 9v
C = 20 µF ,R = 100
1
a) time constant t = R X C
t = 100 X 20 X 10-6
t = 2 X 10-3 sec
b)
the maximum charge on the capacitor
q = C X v
q = 20 X 10-6 X 9
q = 0.18 X 10-3 C
c)
the charge on the capcitor after two time constant
v X ( 1-e-2 ) = 9 X (1-e-2 )
= 9 ( 1 - 0.135)
= 9 X 0.865
= 7.785 v
2.
the charge on the capcitor after 0 to 6 time constants are
v X ( 1-e-0 ) = 9 X (1-e-0 )
at t = 0 , v = 0 V
t = 1 , v X ( 1-e-1 ) = 9 X (1- 0.36 )= 5.76 V
t = 2 , v X ( 1-e-2 ) = 9 X (1- 0.135 )= 7.785 V
t = 3 , v X ( 1-e-3 ) = 9 X (1- 0.049 )= 8.559 V
t = 4 , v X ( 1-e-4 ) = 9 X (1- 0.018 )= 8.838V
t = 5, v X ( 1-e-5 ) = 9 X (1- 0.0067 )= 8.93V
t = 6 , v X ( 1-e-6 ) = 9 X (1- 0.00247 )= 8.97 V
3.
power = E X I
= 120 X 2
= 240 watts
= 240 Joule / sec
Q = m X c X T
Q = 0.500 X 4186 X (100-23)
Q = 140231J
or
Q = 140.231 kJ
then the time is
t = 140.231 X 103 / 240
t = 584 .29sec
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