Phys201
Review Problems
–
Ch30
Page 7
14.
Two long straight wires carry currents perpendicular to the
xy
plane. One carries a current of 50 A
and passes through the point
x
= 5.0 cm on the
x
axis. The second wire has a current of 80 A and
passes through the point
y
= 4.0 cm on the
y
axis. What is the
magnitude
of the resulting magnetic
field at the origin?
Ans: 450μT
16.
A current path shaped as shown in Figure P30.13 produces a magnetic field at P, the center of the
arc. If the arc subtends an angle of
θ
5=30.0
o
and the radius of the arc is0.600 m, what are the magnitude
and direction of the field produced at P if the current is 3.00 A?
Ans: 262nT

Phys201
Review Problems
–
Ch30
Page 8
17
. A long, straight wire carries a current I. A right-angle bend is made in the middle of the wire. The
bend forms an arc of a circle of radius r as shown in Figure P30.1 Determine the magnetic field at point
P, the center of the arc.
Ans: 0.28415 μo I/r
18. The drawing shows four insulated wires overlapping one another, forming a square with
0.050-m sides. All four wires are
much longer (long wires)
than the sides of the square. The net
magnetic field
at the center
of the square is 61 μT.
Calculate
the current
I
.

Phys201
Review Problems
–
Ch30
Page 9
19. Two long, straight wires are separated by 0.120 m. The wires carry currents of 8.0 A
in opposite directions, as the drawing indicates. Find the magnitude of the net magnetic
field at the points labeled
(a)
A
and
(b)
B
.
20. The drawing shows two perpendicular, long, straight wires, both of which lie in the
plane of the paper. The current in each of the wires is I = 5.6 A. Find the magnitudes of
the net magnetic fields at points A and B.

Phys201
Review Problems
–
Ch30
Page 10
21. The triangular loop of wire shown in the drawing carries a current of I = 4.70 A.

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