What is this the smallest magnetic field Feynman could use During a demonstratio

Question

What is this the smallest magnetic field Feynman could use During a demonstration, Feynman has hidden an electromagnet under a table. On the table surface (assumed to be horizontal), he places a wire with a mass density of 0.90 g/cm. The coefficient of static friction between the wire and surface is 0.250. Feynman then connects the wire to a battery such that a current of 1.50 A flows westward. To Layman's amazement, the wire starts to move miraculously. The motion is southward. What is the smallest magnetic field (direction and magnitude) Feynman could use to pull this "trick" on Layman?

Explanation / Answer

Smallest magnetic field which balances the force of friction.

So,

Frictional force = Force due to magnetic field

miu*m*g = B*I*L

let length be L cm,them m = 0.9*L gm = 9L *10^-4 Kg

putting values:

miu*m*g = B*I*L

0.25*9L *10^-4*9.8 = B*1.5*L

B=1.47*10^-3 T

Answer: 1.47*10^-3 T

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