The Biot-Savart law asserts that the magnetic field dB due to an
element dl carrying a steady current I at a point P at a distance r from
the current element is:
0
d3
d
4
I
r
µ
×
=
π
l
r
B
To obtain the total field at P, we must integrate this vector expression
over the entire length of the conductor 5 The magnitude of the magnetic field due to a circular coil of radius R
carrying a current I at an axial distance x from the centre is
EXAMPLE 4 13
Solution
(a) Total resistance in the circuit is,
3
63
RG
+
=
Ω