A horizontal wire `0*1m` long carries a current of `5A`. Find the magnitude and direction of the magnetic field, which can support the weight of the wire. Given the mass of the wire is `3xx10^-3 kg//m` and `g=10ms^-2`.

Options

A. `6xx10^-3T`, acting vertically upwards
B. `6xx10^-3T`, acting horizontally perpendicular to wire
C. `6xx10^-2T`, acting vertically downwards
D. `6xx10^-2T`, acting horizontally perpendicular to wire

Answer

B

Explanation

Here, mass of wire `m=0*1xx(3xx10^-3)kg`,
`I=5A`, `B=?`, `l=0*1m`
In equilibrium position, `F=IlB=mg`
or `B=(mg)/(Il)=((0*1xx3xx10^-3)xx10)/(5xx0*1)=6xx10^-3T`
The weight of wire can be supported by force F if it is acting vertically upwards (i.e. opposite to the weight of wire). It will be so if the direction of `vecB` is horizontal and perpendicular to wire carrying current.