Summary

• Faraday's law
• Lenz's law

• Written Quiz    Timer
  
  
• Faraday's Law
  • magnetic flux applet
  • equation
    
    Example #1
    
    Example #2
    
    
  • EMF induced in a moving conductor applet
    
    Example #3
    
  
  
• Motors & generators revisited

gc6 tb21.5
Doubling the diameter of a loop of wire produces what kind of change on the induced emf, assuming all other factors remain constant?
A. The induced emf is four times as much.
B. The induced emf is twice as much.
C. The induced emf is half as much.
D. There is no change in the induced emf.
Answer







sj6 31.6
In what time must a 0.20 T magnetic field be turned off in order to induce a 10 kV emf in a solenoid of 500 turns and 10 cm diameter?
A. 5.33 µs           B. 78.5 µs
C. 335 µs            D. 22.2 ms
Answer







sj6 31.21
A 1.2 m frictionless bar slides in a 2.5 T magnetic field as shown. If R = 6.0 W, what force is needed to keep the bar sliding at 2.0 m/s?
A. 3.00 N            B. 1.00 N
C. 0.500 N          D. 0.025 N
Answer







 



A. The induced emf is four times as much.
The magnetic flux is proportional to the area, which will increase by a factor of four when the diameter is doubled. The change is flux will then be four times larger, and so will the induced emf.












 



B. 78.5 µs













 



A. 3.00 N