Help w/ RC circuits phsyics?

Question

can someone explain the answer to question 2?

http://class.phys.psu.edu/212Recitations/07_Circuits/RC_Circuits.pdf

Answer 1

after several time constants, the capacitor has zero current and the voltage will be set by the other devices. In this case, it will have 40 volts across it. Using V=I*R
40=I*20 I=2 Amp.

to find Q Use C=Q/V

V=40 and C is provided in the diagram

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Answer 2

i visit anticipate which you meant for 240VAC to be utilized to the circuit. It DC became into utilized the reaction interior the circuit could purely be short and could purely final for 5 time constants. Case a million: The impedance Zt = 500 -j500 or 707@perspective -40 5 assuming that the voltage is240Vac @ perspective of 0 deg then Ptotal = Et^2/Z = (240@perspective 0)^2/707@perspective -40 5 = 80 one.47VA@perspective 40 5 the authentic potential of the circuit is the potential dissipated interior the resistor that's comparable to Ptotal cos 40 5= 80 one.47VA X .707 = fifty seven.6W Case 2: from above Z= 707@perspective -40 5 I(total) = Et/Z = 240 @perspective 0/707@perspective-40 5 = .339Amps @ perspective 40 5 authentic potential = potential in resistor and Pr = I(total)^2 x R = (.339)^2 x 500 = .one hundred fifteen x 500 = fifty seven.62Watts

Answer 3

A long time after the switch is closed, (like one second) the capacitor is fully charged but there is no flow through it. This becomes a simple resistor circuit.