Question

On oscillating any metallic sphere in a magnetic field, its oscillatory motion is:

• A. Accelerated
• B. Damping
• C. Uniform
• D. None of these

Hint:

Eddy currents in conductors in a magnetic field cause damping of oscillations by converting mechanical energy into heat.

Answer 1

The Correct Option is B

When a metallic sphere oscillates in a magnetic field, it experiences a changing magnetic flux through its body due to its motion. According to Faraday’s law of electromagnetic induction, this changing magnetic flux induces circulating currents within the conductor called eddy currents. These eddy currents generate their own magnetic fields that oppose the change in the original magnetic flux, as stated by Lenz’s law. The interaction between the induced magnetic fields and the external magnetic field creates a force opposing the motion of the sphere. This opposing force acts like a damping force, converting the mechanical energy of oscillation into heat energy within the conductor due to the resistance faced by the eddy currents. As a result, the amplitude of the oscillations decreases gradually over time, causing the oscillations to damp. Thus, eddy currents are responsible for the energy loss and gradual reduction in oscillation amplitude when a metallic sphere oscillates in a magnetic field.