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)

Suppose this page is perpendicular to a uniform magnetic field and the magnetic flux through it is 5Wb. If the page is turned by 30◦ around an edge the flux through it will be: A. 2.5Wb B. 4.3Wb C. 5Wb D. 5.8Wb E. 10Wb

A car travels northward at 75 km/h along a straight road in a region where Earth’s magnetic field has a vertical component of 0.50 × 10 −4 T. The emf induced between the left and right side, separated by 1.7m, is: A. 0 B. 1.8mV C. 3.6mV D. 6.4mV E. 13mV

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Circuit element Average Power ReactancePhase of currentVoltage 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 SUMMARY ( )

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Power Station Transmission lines E rms =735 kV, I rms = 500 A home 110 V T1T1 T2T2 Step-up transformer Step-down transformer R = 220Ω ( )

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Hitt A generator supplies 100 V to the primary coil of a transformer. The primary has 50 turns and the secondary has 500 turns. The secondary voltage is: A V B. 500 V C. 250 V D. 100 V E. 10V

hitt The main reason that alternating current replaced direct current for general use is: A. ac generators do not need slip rings B. ac voltages may be conveniently transformed C. electric clocks do not work on dc D. a given ac current does not heat a power line as much as the same dc current E. ac minimizes magnetic effects