Force on a Current Carrying Conductor Placed
in the Magnetic Field
• Uniform magnetic field between the two
opposite poles
S
N
Fig.(a) Main magnetic field
S
N
Fig (b)
1
N
S
FORCE
FIG. (c)
FORCE
N
S
Fig. (d)
2
Torque in DC Motor
(i) when unit vector n is perpendicular to the field
The Lorentz force equation,
3
(d) The force on section SP
The net force on the rectangular loop is
The net torque due to these forces about an axis passing through
the center
Since, A = ab is the area of the
rectangular loop PQRS, the net torque
for this configuration is
4
(ii) when unit vector n is at an angle θ with the field
5