4. 21. (a) A straight horizontal conducting rod of length 0.45 m and mass 60 g is suspended by two vertical wires at its ends. A current of 5.0 A is set up in the rod through the wires. What magnetic field should be set up normal to the conductor in order that the tension in the wires is zero?
In order for the tension in the wires to be zero the force due to the magnetic field must be equal to the gravitational force on the rod.
mass of rod=0.06 g
length of rod=0.45m
the current flowing through the rod=5 A
A magnetic field of strength 0.261 T should be set up normal to the conductor in order that the tension in the wires is zero