5 m = y, 
7
0
T m
/4
10
A
µ
−
π =
q = 90° ; sin q = 1
7
2
2
10
10
10
d
25
10
−
−
−
×
×
=
×
B
= 4 × 10–8 T
The direction of the field is in the +z-direction This is so since,
ˆ
ˆ
d
 
×
i ×
j
x
y
r
l
(
)
ˆ
ˆ
y
x
=
∆
i × j
ˆ
y
x
=
∆ k
We remind you of the following cyclic property of cross-products,
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
;
;
×
=
×
=
×
=
i
j
k
j
k
i k
i
j
Note that the field is small in magnitude In the next section, we shall use the Biot-Savart law to calculate the
magnetic field due to a circular loop 4