Question

What is the effect of eddy currents in the aluminium disc?

(a) varies by a factor of twice the disc length

(b) independent of the disc speed

(c) varies by a factor of four times the disc size

(d) proportional to the disc speed

This question was posed to me in an interview.

My question is from Induction Type Single Phase Energy Meter topic in section Measurement of Power and Related Parameters of Electrical Measurements

Answer 1

The correct choice is (d) proportional to the disc speed

The explanation: The eddy currents induced in an aluminium disc vary in proportion to the speed of the disc. As a result the braking torque exerted on the disc varies in proportion to the speed.