A straight horizontal conducting rod of length `0*45m` and mass `60g` is suspended by two vertical wires at its end. A current of `5*0A` is set up in the rod through the wires. (a) What magnetic field should be set up normal to the conductor inorder that the tension in the wires is zero? (b) What will be the total tension in the wires if the direction of current is reversed, keeping the magnetic field same as before. (Ignore the mass of the wire) `g=9*8ms^-2`.

Explanation

Length of the rod, `l = 0.45m`
Mass suspended by the wires, `m = 60g = 60 xx 10^(-3)kg`
Acceleration due to gravity, `g = 9.8 m//s^(2)`
Current in the rod flowing through the wire, `I = 5A`
(a) Magnetic field (B) is equal and opposite to the weight of the wire i.e.,
`Bll = mg`
`:. B = (mg)/(ll)`
`= (60 xx 10^(-3) xx 9.8)/(5 xx 0.45) = 0.26 T`
A horizontal magnetic field of `0.26T` normal to the length of the conductor should be set
`=0.26 xx 5 xx 0.45 xx (60xx 10^(-3)) xx 9.8`
`=1.176 N`