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. (a) What magnetic field should be set up normal to the conductor in order 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?

Explanation

(a) For zero tension in the wire,
`F=mg, m=60 times 10^(-3)kg`.
i.e., `BIL sin90^(@)=mg, g=10ms^(-2)`
or `" "(mg)/(IL)=(6 times 10^(-2) times 10)/(5 times 0.45)T`
i.e., `" "`B=0.27T
If the direction of current is reversed,
net force acting downwards = BIL+mg
`" "mg+mg`
`" "=2mg`
`" "=2 times 0.06 times 10`
`" "=0.12 times 10`
`" "=1.2N" "("Tension"(T_(1)+T_(2))` in the wires
`" "=1.2N.`