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1  

A  square  loop  of  wire  carrying  current  I  is  in  a  uniform  magne;c  field  B.    The  loop  is  perpendicular  to  B  (B  out  of  the  page).      What  is  the  direc;on  of  the  net  force  on  the  wire  loop?

A: out of the page B: into the page C: é D: ê E: 0 (or, none of these)

B

I

A  square  loop  has  a  CCW  current.  It  sits  in  a  uniform  B  field  (OUT  of  the  page)    Note:  the  B  field  is  "cut  off"  partway  up  the  current  loop    What  is  the  direc;on  of  F(net)  on  the  whole  loop?  

A)    B)  C)  é  D) ê  E)  other  

No B field out here

I

E Other

A rectangular loop of wire (with CW current i ) is near a long straight wire carrying current I. What is the direction of the net force on the rectangular loop, due to the B-field from the long, straight wire?

Current  loop:  Which  way  is  B(center)  poin;ng?  

I (Front)

I (back)

3/6/15  

2  

Current  loop:  Which  way  is  B(center)  poin;ng?  

I (Front)

I (back) B (center)

N

S

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3  

A  current-­‐carrying  loop  of  wire  can  pivot  on  a  fric;onless  axis  through  its  center.    There  is  a  uniform  magne;c  field  B  poin;ng  right.  How  does  the  loop  move?      

B

axis

I

A: Slides right.

B: twists, right edge towards you. C: twists, left edge towards you. D: Nothing, no torques, no forces.

A  bar  magnet  is  placed  near  a  rectangular  loop  of  wire  carrying  a  current  I,  as  shown.    The  loop  can  rotate  freely  about  the  axis.  (Shown  dashed)

   

The loop tends to rotate so that the right edge: A: Shifts sideways B: rotates towards you C: rotates away D: no motion

A  bar  magnet  is  placed  near  a  rectangular  loop  of  wire  carrying  a  current  I,  as  shown.    The  loop  can  rotate  freely  about  the  axis.  (Shown  dashed)

 

 

The loop tends to rotate so that the right edge: A: rotates towards you B: rotates away C: no motion

B

Magne;c  moment:  

μ    =  I*Area  of  loop  points  normal  to  area,    like  B(center)  

I (Front)

I (back) µ

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4  

What  is  the  current  direc;on  in  this  loop  (viewed  from  above?)    And  which  side  of  the  loop  is  the  north  pole?

A) CW; N on top B) CCW: N on top C) CW: N on bottom D) CCW: N on bottom

The  compass  magnet  has  a  Dipole  Moment  poin;ng  along  the  RED  arrow  (North  End  of  the  Magnet).  What  is  the  direc;on  of  the  rota;on  for  this  compass?    A)   CW  B)   CCW  C)   There  is  no  net  torque

B

Two  loops  of  wire  have  current  going  around  in  the  same  direc;on.  The  forces  between  the  loops  is:

A: Attractive B: Repulsive C: Net force is zero.

i1

i2

Two  loops  of  wire  have  current  going  around  in  opposite  direc;ons.  The  forces  between  the  loops  is:

A: Attractive B: Repulsive C: Net force is zero.

i1

i2

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5  

Solenoid: A long coil of wire consisting of many loop of wire

x

L