Electromagnetic Oscillations and Alternating Current Chapter 31 Electromagnetic Oscillations and Alternating Current In this chapter we will cover the following topics: -Electromagnetic oscillations in an LC circuit -Alternating current (AC) circuits with capacitors -Resonance in RCL circuits -Power in AC-circuits -Transformers, AC power transmission (31 - 1)

C. 140 T/s, increasing D. 420 T/s, decreasing E. 420 T/s, increasing HITT The circuit shown is in a uniform magnetic field that is into the page. The current in the circuit is 0.20 A. At what rate is the magnitude of the magnetic field changing? Is it increasing or decreasing? 12cm x 12 cm, 4V, 10Ω Zero B. 140 T/s, decreasing C. 140 T/s, increasing D. 420 T/s, decreasing E. 420 T/s, increasing Χ B

L C (31 - 2)

L C (31 - 3)

L C (31 - 4)

1 2 3 4 5 6 7 8 (31 - 5)

(31 - 6)

(31 - 7)

(31 - 8)

L C (31 - 9)

(31 - 10)

(31 - 11)

(31 - 12)

O (31 - 13)

(31 - 14)

O (31 - 15)

(31 - 16)

SUMMARY Circuit element Average Power Reactance Phase of current Voltage amplitude Resistor R Current is in phase with the voltage Capacitor C Current leads voltage by a quarter of a period Inductor L Current lags behind voltage by a quarter of a period (31 - 17)

(31 - 18)

O A B (31 - 19)

O A B (31 - 20)

(31 - 21)

(31 - 22)

(31 - 23)

(31 - 24) Transmission lines Erms =735 kV , I rms = 500 A home Power Station Transmission lines Erms =735 kV , I rms = 500 A home 110 V T1 T2 Step-up transformer Step-down transformer R = 220Ω (31 - 24)

(31 - 25)

(31 - 26)

(31 - 27)

hitt A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is charged. If T is the period of the resulting oscillations, the next time after t = 0 that the charge on the capacitor is a maximum is: A. T B. T/4 C. T/2 D. T E. 2T