Today4/10

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Today4/10

• Current Loops
• Phantom magnets
• Force/torque on loops in a B-field
• HW 4/10 Force on Loops Due Monday, 4/14

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B Fields - Current Loop
Current loops
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B Fields - Magnet
Current loops are magnets!!! Behave like
magnets!!!
S
N
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B Fields - Current Loop
Current loops
Phantom Bar Magnet
N
S
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Magnetic Torque, Loops
What happens to loop?
Turn the loop into a magnet. Magnets line up
with the field. (A compass needle is a magnet!)
Loop is a magnet (needle) centered in the loop
with the N pole facing away from you.
The loop (magnet) will rotate so it lines up
with the field. (S up and out of the page)
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Magnetic Torque, Loops
What happens to loop?
Turn the loop into a magnet. Magnets line up
with the field. (A compass needle is a magnet!)
Loop is a magnet (needle) centered in the loop
with the N pole facing away from you.
S
N
The loop (magnet) will rotate so it lines up
with the field. (S up and out of the page)
This is a torque on the loop.
7
A bar magnet and current loop (powered by a
battery) are shown in various orientations below.
In each case the magnet if held in place and the
current loop is released and allowed to rotate
only about the axis shown. Determine if the loop
will rotate. If so, find the direction of
rotation and how far it rotates. If the loop is
in unstable equilibrium, say so. (RHR 3)
Clockwise (viewed from above) 90North out
Torque clockwise from above, cant turnNorth out
Clockwise (viewed from above) 90North in
Unstable equilibrium small tap will cause a 180
flip either direction. North right
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Magnetic Force, Loops
What happens to loop?
Turn the loop into a magnet. Like poles repel.
real magnet
Loop is a magnet (needle) centered in the loop
with the N pole facing away from you.
S
N
Unlike poles attract so the loop is attracted,
force on loop is to the left.
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Magnetic Force, Loops
What happens to loop?
Turn the loop into a magnet. Like poles repel.
real magnet
Loop is a magnet with the N pole facing left
S
N
Like poles repel so the loop is repelled, force
on loop is to the right.