The horizontal rails are 30 cm apart. On them lies a rod weighing 100 grams perpendicular to the rails.

The horizontal rails are 30 cm apart. On them lies a rod weighing 100 grams perpendicular to the rails. The whole system is in a vertical magnetic field with an induction of 0.5 T. When passing a current of 2 A through the rod, it moves with an acceleration of 2 m / s². Find the coefficient of friction between the rails and the bar.

The ampere force acts on a rod with a current in a magnetic field:

FA = IBL sin a,

where I is the current,

B – magnetic field induction,

L – conductor length,

a is the angle between the vector of magnetic induction and the direction of the current.

The friction force Ft is directed against the force FA. The resulting force FА – Fт makes the staff move with acceleration a:

FА – FT = ma,

where m is the mass of the rack.

IBL sin a – FT = ma;

Fт = IBL sina – ma.

The response of the laths to the rod N is equal in absolute value to the weight of the rod P:

| N | = | P | = mg.

Answer: μ = 0.1.