Summary

• Vector cross products
• Magnetic force on charges
• Magnetic force on currents

• Written Quiz Ch. 27





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Chapter 29

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• The Biot-Savart Law
• Single wire field applet
• The field of a loop of current

• Two right-hand rules
• Right hand rule animation
• B field applet

Example #1
Example #2
Example #3


  


• Ampere's law introduction



• Practice:
  Try these additional examples
Example #4

Example #5

Example #6



• Prepare:
  Tomorrow's lecture contains a video review of chapters 28-29

klm
A wire carries an electrical current toward the north. In which direction does B point directly above the wire?
A. North
B. South
C. East
D. West
E. Upward
F. Downward
Answer















Knight2 33.stt.4
The current in this loop flows _____ as seen from above, and the north magnetic pole of its field is on the _____ side of the loop.
A. clockwise ... top
B. clockwise ... bottom
C. counterclockwise ... top
D. counterclockwise ... bottom
Answer



















POP5 22.35
What is the magnetic field at P in the figure if the radius of the curve is 0.60 m and the current is 3.00 A?
A. 5.75 µT
B. 572 nT
C. 262 nT
D. 108 nT
Answer























gc6 20.26
A jumper cable used to start a stalled vehicle carries a 65 A current. How strong is the magnetic field 6.0 cm away from it?
A. 2.17×10⁻⁴ T
B. 6.90×10⁻⁵ T
C. 3.45×10⁻⁵ T
D. 1.38×10⁻⁶ T
Answer















Walker5e fig 22-32
Two current-carrying wires cross at right angles, as shown. At which points will the magnetic field be the strongest?
A. Point 3
B. Points 1 and 2
C. Points 1 and 3
D. Points 2 and 4
Answer























Walker5e CnEx 22-12
The magnetic field shown below is due to the horizontal, current-carrying wire. Which way does the current in the wire flow?


A. to the left
B. to the right
C. either direction produces the same magnetic field
Answer



























 
A. +21.0 V
























 



C. East
Using the right-hand-rule, point your thumb toward the north, the same direction as the current. The curled fingers of your right hand would point east directly above the wire.




















 



B. clockwise ... bottom

The second right-hand rule states that if the fingers of your right hand curl in the direction of the current, your thumb points in the direction of the magnetic field at the center of a current loop. If you point your right thumb downward with the depicted field, your fingers curl clockwise. Because magnetic field lines flow out of the north pole and into the south, we conclude the north pole is at the bottom of the loop.




















 



C. 262 nT
























 



A. 2.17×10⁻⁴ T

That's equivalent to 217 µT, about four times stronger than Earth's magnetic field.




















 



D. Points 2 and 4
Using the right-hand-rule, you can find the magnetic fields due to the currents are each out of the page on the right side of the vertical wire, and above the horizontal wire. This means the two fields tend to add at points 2 (each out of the page) and 4 (each into the page), and tend to cancel at points 1 and 3.





















 



A. to the left
Using the right-hand-rule, your fingers point into the page above the wire and out of the page below the wire when your thumb points toward the left. That is the direction of the electric current in the wire.