A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to cancel the weight of the rod?

Question

Quizplus · Accepted Answer

The magnetic force (F) on the rod is given by F = BIL, where B is the magnetic field, I is the current, and L is the length of the rod. The weight (W) of the rod is given by W = mg, where m is the mass and g is the acceleration due to gravity (approximately 9.8 m/s²). Setting the magnetic force equal to the weight for equilibrium: BIL = mg. Solving for I gives I = mg / (BL) = (0.050 kg * 9.8 m/s²) / (0.10 T * 1.0 m) = 4.9 A.

A Thin Copper Rod 1