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 5 MAGNETIC FIELD ON THE AXIS OF A CIRCULAR
CURRENT LOOP
In this section, we shall evaluate the magnetic field  due
to a circular coil along its axis