Electrical Engineering ⇒ Topic : Force between two Conductors Carrying Currents

FORCE BETWEEN TWO CONDUCTORS CARRYING CURRENTS

Figure 1 (a) and 1(b) show that the two conductors A and B carry current in the same direction and in the opposite direction, respectively. When they carry current in the same direction, the flux

distribution is exhibited in Figure 1 (a). The magnetic fields set up by the two conductors are in opposite direction. Hence, they attract each other. When they carry current in opposite direction, the flux distribution is shown in Figure 1 (b). The magnetic fields set up by two conductors are in same direction. Hence they repel each other.

                                                                                          figure (1)

FORCE BETWEEN PARALLEL CONDUCTORS AMPERE'S LAW

                                                         ...........  (a)

where F = force between two parallel conductors

    I₁ , I₂ = currents flowing through two parallel conductors

            l = length of each conductor, and

cf         d = distance between the conductors.

Eqn. (a) is known as Ampere's law and is used to define the ampere in S.I. units

If I=d=l m;I₁ =I₂= 1A,then F=2 x 10^-7

Hence, one ampere is defined as follows:

"An ampere is that current when flowing in each of the two in finitely long parallel conductors situated in vacuum and separated 1 metre between centres, produces on each conductor a force of 2 x 10^-7 N per metre length".

                        Fig. (a) Force between two parallel conductors