Summary

• Faraday's law
• Inductors
• Energy in magnetic fields

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Chapter 33

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• Maxwell's equations, video
1. Gauss's Law (generalized Coulomb's Law)
E field lines diverge from positive charges
2. Gauss's Law for magnetism
B field lines always make closed loops (no monopoles)
3. Faraday's Law
changing B produces a changing E
4. Ampère's Law
currents and changing E fields can each produce B fields







• EM waves
• wave equation

• animated applet
• speed
• amplitude ratio
• right-hand rule

Example #3



• Accelerating charges produce EM waves
• Radio waves applet



• The electromagnetic spectrum
  
  
  
  
• Practice:
  Try these additional examples
Example #4

Example #5



• Prepare:
  Read textbook sections 33-1 through 33-3 before the next lecture

POP5 24.4
A fixed inductance L = 1.05 µH in an LC circuit is connected in series with a variable capacitor to tune to a 6.30 MHz broadcast. What is C?
A. 608 pF
B. 1.18 nF
C. 38.5 nF
D. 6.55 µF
Answer



















klm
At time t = 0 the switch is closed in the circuit below when the capacitor is fully charged. If C = 15.0µF and L = 15.0 mH, what is the first time the capacitor will be fully discharged?
A. 328 ms
B. 633 ns
C. 745 µs
D. Never!
Answer















POP5 24.12
An electromagnetic wave in vacuum has an electric field amplitude of 220 V/m. Calculate the amplitude of the corresponding magnetic field.
A. 2.53 mT
B. 429 µT
C. 55.8 nT
D. 733 nT
Answer















Walker5e 25.01
If the electric field in an electromagnetic wave is increasing in magnitude at a particular time, the magnitude of the magnetic field at the same time is _____.
A. increasing
B. decreasing
C. staying the same
Answer



















Walker5e 25.02
The electric field of an electromagnetic wave points in the positive y direction. At the same time, the magnetic field of this wave points in the positive z direction. In what direction is the wave traveling?
A. negative x direction
B. negative y direction
C. negative z direction
D. positive x direction
Answer































 



A. 608 pF






















 
C. 745 µs






















 



D. 733 nT






















 



A. increasing
The electric and magnetic fields are correlated to each other; when one increases, so does the other. Refer either to Figure 25-4 or to Equation 25-9, E = cB.




















 



D. positive x direction
Point the fingers of your right hand in the direction of E (positive y direction) and curl your fingers toward B (positive z direction), and your thumb points in the direction of propagation (positive x direction).