Page 12 - Teach Yourself Electricity and Electronics

xii Contents

14 Capacitive reactance 247
Capacitors and direct current 247
Capacitors and alternating current 248
Reactance and frequency 249
Points in the RC plane 251
Vectors in the RC plane 253
Current leads voltage 254
How much lead? 256
Quiz 259

15 Impedance and admittance 264
Imaginary numbers 264
Complex numbers 265
The complex number plane 266
The RX plane 269
Vector representation of impedance 270
Absolute-value impedance 272
Characteristic impedance 272
Conductance 275
Susceptance 275
Admittance 276
The GB plane 277
Vector representation of admittance 279
Why all these different expressions? 279
Quiz 280

16 RLC circuit analysis 284
Complex impedances in series 284
Series RLC circuits 288
Complex admittances in parallel 289
Parallel GLC circuits 292
Converting from admittance to impedance 294
Putting it all together 294
Reducing complicated RLC circuits 295
Ohm’s law for ac circuits 298
Quiz 301

17 Power and resonance in ac circuits 305
What is power? 305
True power doesn’t travel 307
Reactance does not consume power 308
True power, VA power and reactive power 309
Power factor 310
Calculation of power factor 310
How much of the power is true? 313