Question

A wire of length L and mass m rests horizontally on a table (under the influence of the gravitational force). It carries a current I. Find the minimum magnitude B of the magnetic field necessary to lift the wire off the table. Group of answer choices ILg/m mgI/L2 IL/(mg) mg /(IL)

Answer 1

The wire experiences 2 vertical forces when it lifts up:

1. force due to gravity = mg downwards,where m is mass and g is gravitational acceleration.

2. Force due to magnetic field = ILB upwards, where I is current in the wire, L is length of wire and B is magnetic field.

To lift the wire, upward force downward force

=> ILB   mg

=>B   mg/IL)

So,minimum magnetic field to lift the wire is given by: mg/(IL)