A wire segment 1.2 m long carries a current I = 3.5 A and is oriented as shown in the figure.A uniform magnetic field of magnitude 0.50 T pointing toward the -x direction is present as shown.The +z-axis points directly into the page.What is the magnetic force vector on the wire segment?
A) +1.6 N
B) -1.6 N
C) +1.6 N
D) (+1.3 - 1.6 ) N
E) (-1.3 + 1.6 N

Question

A wire segment 1.2 m long carries a current I = 3.5 A and is oriented as shown in the figure.A uniform magnetic field of magnitude 0.50 T pointing toward the -x direction is present as shown.The +z-axis points directly into the page.What is the magnetic force vector on the wire segment? 
A) +1.6 N 
B) -1.6 N 
C) +1.6 N 
D) (+1.3 - 1.6 ) N 
E) (-1.3 + 1.6 N

Quizplus · Accepted Answer

The magnetic force on a current-carrying wire segment is given by: 
F = I L x B
where F is the force vector, I is the current, L is the length of the wire segment, and B is the magnetic field vector. The cross product gives the direction of the force vector.
In this case, I = 3.5 A, L = 1.2 m, and B = -0.50 T i (where i is the unit vector in the x direction).
So, 
F = (3.5 A)(1.2 m) x (-0.50 T i) = -2.1 N j
The cross product of L and B points in the +y direction, so the y-component of the force vector is positive. Therefore, 
F = +2.1 N j
which is closest to answer choice C (+1.6 N).

A Wire Segment 1