HW4answers - v / t t = C v / i = (2000E-6)(100)/(100E-6) =...

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HW 4 answers P3.1 – Describe the construction of capacitors. Answer – Capacitors consist of two parallel thin plate conductors separated by a thin layer of insulating material. P3.3 – If the voltage across a capacitor is constant, what is the value of the current? Explain why. Answer – Because i = C dv/dt for a capacitor, the current is zero if the voltage is constant. Thus we say that capacitances act as open circuits for constant DC voltages. P3.4 – The voltage across a 100 uF (microfarad) capacitor is 200 V. What is the magnitude of the net charge stored on each plate? What is the total net charge stored on both plates? Answer – The net charge on each plate is Q=CV=(100e-6)x200=.02 C. One plate has a net positive charge and the other has a net negative charge so the net charge for both plates is zero. Answer: i = C dv/dt = C ∆
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Unformatted text preview: v / t t = C v / i = (2000E-6)(100)/(100E-6) = 2000 sec P3.36 Describe the construction of inductors. Answer Inductors consist of coils of wire wound on coil forms such as toroids. P3.37 If the current through an inductor is decreasing in magnitude, is the energy flowing into or out of the inductor? Answer Because the energy stored in an inductor is W= Li 2 , the energy stored in the inductor decreases when the current magnitude decreases. Therefore, the energy is flowing out of the inductor. P3.38 If the current through an inductor is constant, what is the value of the voltage across the inductor? Explain why. Answer Because v L ( t ) = L di L ( t )/ dt , the voltage is zero when the current is constant. Thus we say that inductors act as short circuits for steady DC currents....
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