hitt

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hitt

• Two long straight wires pierce the plane of the
  paper at vertices of an equilateral triangle as
  shown. They each carry 3A in the same direction.
  The magnetic field at the third vertex (P) has
  the magnitude and direction (North is up)
• (1) 20 µT, west (2) 17 µT, east (3) 15 µT, north
  (4) 26 µT, south (5) none of these

P
4 cm
4 cm
2
Long, straight, parallel wires carry equal
currents into or out of page. Rank according to
the magnitude of the force on the central wire,
largest to smallest.
1. d, c, a, b 2. a, b, c, d 3. b, c, d, a 4. c,
a, b, d 5. b, d, c, a
3

• A horizontal power line carries a current of 5000
  A from south to north. Earth's magnetic eld (60
  µT) is directed towards north and inclined
  down-ward 50 degrees to the horizontal. Find the
  magnitude and direction of the magnetic force on
  100 m of the line due to the Earth's field.
• 23 N, west (2) 23 N, east (3) 30N, west
• (4) 30N, east (5) none of these

I
50
N
B
4
Chapter 30 Induction and Inductance In
this chapter we will study the following topics
-Faradays law of
induction
-Lenzs rule

-Electric field
induced by a changing magnetic field
-Inductance and mutual
inductance
- RL circuits

-Energy stored in a
magnetic field
(30 1)
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(30 6)
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(30 8)
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(30 9)
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(30 10)
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(30 13)
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(30 15)
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(30 17)
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(30 19)
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Electrons are going around a circle in a
counterclockwise direction as shown. At the
center of the circle they produce a magnetic
field that is
e
A. into the page B. out of the page C. to the
left D. to the right E. zero
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Long parallel wires carry equal currents into or
out of the page. Rank according to the
magnitude of the net magnetic field at the
center of the square.
1. C,D, (A,B) 2. A, B, (C,D) 3. B, A, C, D 4.
D, (A, B), C
26
Partial Loops (cont.)

• Note on problems when you have to evaluate a B
  field at a point from several partial loops
• Only loop parts contribute, proportional to angle
  (previous slide)
• Straight sections aimed at point contribute
  exactly nothing
• Be careful about signs, e.g.in (b) fields
  partially cancel, whereas in (a) and (c) they add

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(30 4)
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(30 5)