1.  What is the direction of the magnetic field due
to the left wire at the position of the right wire?
A. Left
B. Right
C. Out of page
D. Into page
Right hand rule (see picture)
Correct answer is D
2.  Which one or more of the following choices is
(are) true. A magnetic field:
1. can increase the speed of a moving charge. 2. can decrease the speed of a moving charge.
3. always exerts a force on a moving charge.
4. can exert a force on a moving charge
A. 1 and 3
B. 1 and 2
C. 1, 2, and 3
D. 3
E. 4
Magnetic force is perpendicular to velocity, hence perpendicular to
displacement à no work done à speed does not change à 1 & 2
are wrong. No magnetic force if B and velocity are parallel à 3 is
also wrong. à correct answer is E
3.  A square current loop is placed in a uniform magnetic
field (see the drawing). The dashed line is the axis of
rotation. The magnetic field exerts
A.
C.
A net force and no torque B. No net force and no torque
No net force and a torque D. A net force and a torque
No force on top and bottom segments because B is parallel
or antiparallel to I. On the left segment there is a force
pointing into the page. On the right segment there is a force
of equal magnitude pointing out of the page à no net force
but a non-zero torque à correct answer is C
4.  Cutting a permanent magnet in two pieces....
A. Results always in separate North and South poles
B. Results sometime in separate North and South poles
C. Results in two magnets, each with North and South poles
Correct answer is C (you cannot separate N and S poles)
5.  Two long parallel wires are oriented perpendicular to
the xy plane. They carry the same current I, but in
opposite directions, as shown. The B-field at P points
A. to the right B. to the left C. up D. down E. none of the above
The B field from the bottom wire points in this direction:
The B field from the top wire points in this direction
The sum of the two points to the right à correct answer is A