HOMEWORK for TUESDAY, JULY 12, 2005
For each of the following situations two circuit loops are shown in a uniform
external magnetic field
.
Let the one on the left have a clockwise current
F
t
ext
and the one on the right have a counterclockwise current.
For each loop show
the direction of
.
Determine in each case the forces acting on each side of
F
t
loop
the current and determine if there is a net force or a net torque.
If there is a
net torque, determine how the loop will rotate, and describe how this is related
to the directions of
and
.
F
F
t
t
loop
ext
1.
Œ F
t
ext
Clockwise current on left:
is down
; forces on top, right, bottom,
F
Ð Œ Ñ
t
loop
left sides are, respectively,
,
,
, and
(all directed outward).
There is no
Å
Ä
Æ
Ã
net force and no net torque.
Counterclockwise current on right:
is up
; forces on top, right,
F
Ð Ñ
t
loop
bottom, and left sides are, respectively,
and
(all directed inward).
Æ ß
Ã ß
Å ß
Ä
There is no net force and no net torque.
2.
F
t
ext
Clockwise current on left:
is down
; forces on top, right, bottom,
F
Ð Œ Ñ
t
loop
left sides are, respectively,
and
(all directed inward).
There is no
Æ ß
Ã ß
Å ß
Ä
net force and no net torque.
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 Summer '08
 Fretwell
 Current, Force, Work, Magnetic Field, Fundamental physics concepts, net force, Clockwise

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