I need the answers for all of them with explaining An RC circuit has a resistanc
ID: 1341855 • Letter: I
Question
I need the answers for all of them with explaining An RC circuit has a resistance of 20 M Ohm and a time constant of 100 sec If the capacitor is charged to a voltage of 10v, what is the charge in coulombs on its plates? A charged 1 mu F capacitor is connected in parallel with a 1M Ohm resistor How long after the connection is made will the capacitor voltage drop to a) 50%. b) 10%, and c) 2% of its initial value? How many 1 mu F capacitors would need to be connected in parallel in order to store a charge of 1 coulomb with a potential of 200 volts across the capacitors?Explanation / Answer
1)
resistance = R = 20*10^6 ohms
time constant T = RC = 100 sec
potential difference = v = 10 v
the charge Q = C*V= (T/R)*V = (100/(20*10^6))*10 = 5*10^-5 C <<------answer
(2)
the potential drops with time t as v = Vo*e^-t/RC)
a)
v = 0.5 Vo
0.5 = e^-(t/(1*10^-6*1*10^+6))
t = 0.693 s ,<---answer
(b)
v = 0.1 Vo
0.1 = e^-(t/(1*10^-6*1*10^+6))
t = 2.303 s <---answer
(c)
v = 0.02 Vo
0.02 = e^-(t/(1*10^-6*1*10^+6))
t = 3.912 s <---answer
(3)
Q = Cp*V
Cp = Q/V = 1/200 = 5*10^-3 F
if n capacitane are connected in parallel
Cp = n*C
C = 10^-6
n = Cp/C = (5*10^-3/)/10^-6 = 5000 <<------------answer