The Total solution for NCERT class 6-12
A straight horizontal conductingrod of length 0.45 m and mass 60 g is suspended by two vertical wires at itsends. A current of 5.0 A is set up in the rod through the wires.
(a) Whatmagnetic field should be set up normal to the conductor in order that thetension in the wires is zero?
(b) Whatwill be the total tension in the wires if the direction of current is reversedkeeping the magnetic field same as before? (Ignore the mass of the wires.) g =9.8 m s−2.
Length of the rod, l =0.45 m
Mass suspended by thewires, m = 60 g = 60 × 10−3 kg
Acceleration due to gravity, g =9.8 m/s2
Current in the rod flowingthrough the wire, I = 5 A
A horizontal magnetic field of0.26 T normal to the length of the conductor should be set up in order to getzero tension in the wire. The magnetic field should be such that Fleming’s lefthand rule gives an upward magnetic force.
(b) If the directionof the current is revered, then the force due to magnetic field and the weightof the wire acts in a vertically downward direction.
∴Total tension in the wire = BIl + mg