In: Physics
A 1.08 kg copper rod rests on two horizontal rails 0.84 m apart and carries a current of 60 A from one rail to the other. The coefficient of static friction between rod and rails is 0.53. What is the smallest magnetic field (not necessarily vertical ) that would cause the rod to slide?
A) What is the angle of B from the vertical? (deg)
B) What is the magnitude of B?
A. magnetic force is F = i L B
mg = i L B
force of friction is μ_s ( mg - i L B )
F_s - F = 0
iL B cos θ = μ_s ( mg - iLB sinθ)
B = μs mg / iL ( cos θ + μs sinθ)
θ = tan^-1 (μs)
= tan^-1 ( 0.53)
= 27.9 degrees
B.The smallest value of the magnetic field is
B_min = 0.53 * 1.08*(9.8) / 60 * 0.84 ( cos 27.9 + 0.53 sin 27.9)
= 0.0983 T