7. Two long and parallel straight wires A and B carrying currents of 8.0 A and 5.0 A in the same direction are separated by a distance of 4.0 cm. Estimate the force on a 10 cm section of wire A.
The magnitude of magnetic field at a distance r from a long straight wire carrying current I is given by,
In this case the magnetic field at a distance of 4.0 cm from wire B will be
(I=5 A, r=4.0 cm)
The force on a straight wire of length l carrying current I in a uniform magnetic field B is given by
, where is the angle between the direction of flow of current and the magnetic field.
The force on a 10 cm section of wire A will be
(B=2.5 T, I=8 A, l = 10 cm, =90o)