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# Lecture 12 Electromagnetic Oscillations and Alternating Current Chp. 33 - PowerPoint PPT Presentation

Lecture 12 Electromagnetic Oscillations and Alternating Current Chp. 33. Cartoon -. Opening Demo - Warm-up problem Physlet Topics LC Circuit Qualitatively Electrical and Magnetic energy oscillations Alternating current \Pure R and L, circuti Series RLC circuit Power and Transfomers

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Lecture 12 Electromagnetic Oscillations and Alternating Current Chp. 33

• Cartoon -. Opening Demo - Warm-up problem

• Physlet

• Topics

• LC Circuit Qualitatively

• Electrical and Magnetic energy oscillations

• Alternating current

• \Pure R and L, circuti

• Series RLC circuit

• Power and Transfomers

• Demos

• LR circuit

• Series LRC circuit

Current Chp. 33

B

Axis of rotation

Coil of wire

Where w is the rotational angular

frequency of the generator

w= 2pf and f= 60 Hz

phase Current Chp. 33

Instantaneous voltage

time

Phase constat

Amplitude

Angular frequency

Phasor diagram

L = 4.22mH Current Chp. 33

VR=RI

VL= XLIL or VL= (Lw)Isince I=IL

RL Circuit Example to resistance in DC circuits

Suppose em = 100 volts, f=1000 Hz, R=10 Ohms, L=4.22 mH,

Find XL, Z, I, VR, and Vl.

Power in AC circuits to resistance in DC circuits

Instantaneous power doesn’t mean anything

Need to average over time or one period of the sine wave

Note

Averaging over a sine curve to resistance in DC circuits

Calculate Power lost in resistor from example to resistance in DC circuits

To calculate power produced by the generator you need to take account of the phase difference between the voltage and the current. In general you can write:

For an inductor P = 0 because the phase difference between current through the inductor and voltage across the inductor is 90 degrees

Series LRC circuit to resistance in DC circuits

VR

VC

XC=1/(wC)

VL

XL=wL

ELI the ICE man

Resonance to resistance in DC circuits

Series LRC demo

10 uF to resistance in DC circuits

4.25 mH

Series LCR circuit to resistance in DC circuits