Straight Wire (7, 1)
The magnetic field calculation differs depending upon whether the point is inside or outside the wire.
Equation:
0
r I
- - - - - - - - - - - - - - - - - - - - - - - -
B
=
2
r
Example:
Given:
r=1, rw= 0.25_cm, r=0.2_cm, I=25_A.
Solution: B= 0.0016_T.
Force between Wires (7, 2)
The force between wires is positive for an attractive force (for currents having the same sign).
Equation:
0
r L I b Ia
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -------- -
F b a
=
2
d
Example:
Given: Ia=10_A, Ib=20_A, r=1, L=50_cm, d=1_cm.
Solution: Fba=2.0000E–3_N.
5-32 Equation Reference