Video: Physics Past Exam • 2017/2018 • Pack 1 • Question 35

Physics Past Exam • 2017/2018 • Pack 1 • Question 35

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Video Transcript

In what order do energy transformations in an Inductive Furnace occur? a) Thermal, electrical, magnetic. b) Electrical, thermal, magnetic. c) Magnetic, thermal, electrical. d) Electrical, magnetic, thermal.

To figure out in what order the energy transformations in this furnace occur, we can draw a diagram of an inductive furnace. A furnace of this type consists of a nonconducting chamber which contains chunks of metal. This container is wrapped about by a coil of wire, which carries an alternating current through its loops.

Since this coil of wire is effectively a solenoid as alternating current runs through it, time-varying magnetic fields are set up that pass through the chamber as well as the chunks of metal inside. This changing magnetic field induces in the chunks of metal inside the chamber small loops of current called eddy currents.

These loops of current flow in opposition to the natural resistivity of these chunks of material. In the same way that a light bulb heats up as current passes through it, so do these chunks of metal as the eddy currents work in them. The currents are powerful enough to generate enough heat that the chunks of metal reach their melting point. And this is how these pieces are melted down and mixed together in the nonconducting chamber.

We see then that this process begins with an electrical current leading to the generation of a magnetic field which creates thermal heating in the material in the nonconductive chamber. That order of energy transformations matches up with choice d) electrical, magnetic, thermal.

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